High quality product protection.
For transportation by land, air and sea.
Temporary corrosion protection
in intercontinental trade
Temporary corrosion protection in export packaging
Preserving the value of your goods in intercontinental trade
As they travel to distant countries and far-off continents your products face many challenges. It is
therefore vital that you take effective measures to preserve their value on the journey. We are specialists in this area of export packaging and differentiate between four disciplines:
• External packaging as transport packaging
• Securing packaged goods
• Temporary corrosion protection
• Marking
In this brochure, we would like to introduce you to the most common methods and techniques used
in temporary corrosion protection.
2
CONTENTS
Temporary corrosion protection in export packaging .........................................
What is corrosion? ...........................................................................
Is corrosion always harmful? ..............................................................
How does corrosion occur? ................................................................
Where do the reaction partners come from? ...........................................
How much corrosion is already present before packaging? ...........................
What can we do to prevent corrosion? ..................................................
2
4
5
6
7
8
10
Preparation phases for temporary corrosion ..................................................
Cleaning .....................................................................................
Drying .........................................................................................
Acclimatisation ..............................................................................
11
11
11
11
Desiccant method ..................................................................................
Desiccant ....................................................................................
Barrier layer film to exclude water vapour .............................................
Hygroscopic materials .....................................................................
How to achieve the optimum effect .....................................................
How to monitor effectiveness ............................................................
How to calculate the correct quantity ..................................................
Cost-effectiveness .........................................................................
Advantages and disadvantages of the desiccant method ............................
Practical application of the desiccant method ........................................
12
13
14
15
15
16
16
17
18
19
VCI method .........................................................................................
Mechanism ..................................................................................
Active agents ..............................................................................
Application of the VCI method ..........................................................
How to calculate the correct quantity .................................................
Advantages and disadvantages of the VCI method ...................................
Practical application ......................................................................
VCI barrier layer film impregnated with active agent ...............................
Polyethylene barrier layer film with VCI bubble wrap impregnated with
active agent ................................................................................
Polyethylene barrier layer film with VCI foam impregnated with active agent ..
29
29
30
31
31
31
32
33
33
49
Protective coating method ......................................................................
Application ..................................................................................
Advantages and disadvantages of the protective coating method .................
57
57
58
Important before unpacking ......................................................................
59
What is corrosion?
The term “corrosion” is derived from Latin and describes a “chemical change in the material on the
surface of a solid”. This also implies a change in the material’s properties. DIN 50 900 Part 1 defines
“corrosion” as follows: „The reaction of a metallic material with its environment, which produces
a measurable change in the material and can impair the function of a metallic part or an entire
system.”
With the exception of gold and platinum, all metals and almost all other materials are susceptible
to corrosion. Depending on the corrosion medium (i.e. the medium which attacks the surface, e.g.
solids, liquids, gases), corrosion can also affect plastics, stone, glass and many other materials.
It takes place via a number of pathways: chemical, electrochemical and biotic. In the export packaging business – our core area of expertise – we are primarily concerned with electrochemical corrosion. Consequently, we will limit the discussion of the subject in this brochure to the corrosion of
metals. For the sake of completeness, we should mention that electrochemical corrosion is further
subdivided into anodic (non-ferrous metals) and cathodic (ferrous metals) corrosion reactions. However, for our purposes, this is not important and would involve going into unnecessary detail.
4
Is corrosion always harmful?
Surface corrosion does not always impair the function of the product. For example, it is actually required on structural steel used with concrete. The same applies to aluminium, which has a natural,
protective oxide layer that can be strengthened even further by anodisation. In both these cases,
corrosion does not result in any technical damage.
On the other hand, there are many instances where even the smallest corrosive reaction can cause
very significant damage, e.g. in turbines, bearings, electronic or high precision parts, etc.
In complex assemblies, such as machines and plants, corrosion damage may not always be visible or
on the surface. It can also occur in a system’s interior and essentially remain hidden.
These images show very serious corrosion damage – typical in export packaging.
5
How does corrosion occur?
Most metals do not occur naturally in the form we know them. We almost always encounter them
in their oxidised state. The metals prefer to exist as oxides because it gives them greater chemical
stability. And, although we can use energy to convert them back into their elemental forms, they
strive to return to this lower oxidised energy state with equal vigour.
As soon as it has been manufactured, almost every metal naturally becomes coated with an oxide
layer when it comes into contact with air. This protects it against reacting further with oxygen. We
call this a “passive layer” and its stability depends on the type of metal. Aluminium and zinc have
very stable passive layers. In iron it is fragile, uneven and provides very little protection. In temporary corrosion protection, the primary objective is to protect these passive layers.
Two or more reaction partners are necessary for corrosion to occur. As far as we are concerned, the
most common are water and oxygen. This is known as oxygen corrosion in which oxygen is the corrosive medium reacting with the metal. Here, water plays the role of the electrolyte.
The reaction can be accelerated by the presence of additional substances, such as salts, bases,
alkaline residues or contaminants, sulphides, chlorides, substances containing chlorides, e.g. sweat,
and many others. Dirt can also reinforce reactions. For example, hygroscopically active contaminants can supply the water for the reaction. Bacteria and micro-organisms can also provide reaction
partners in their excreta.
When it comes into contact with an electrolyte, the metal gives up electrons from its surface and
forms metal hydroxides as corrosion products – the precursor to rust. Visible rust then begins to
form including holes and cracks.
AIR
Rust Ring
SALT WATER
IRON
Anodic
Reaction
6
The diagram on the left illustrates the process of
electrochemical oxygen corrosion under a drop of salt
water. The reaction product becomes visible after just
a few minutes.
We view this process as being electrochemical. In other
words, it immediately creates an electrical circuit. It
also means that the exchange of electrons, and therefore the reaction, begins as soon as the current starts
to flow. The first signs of corrosion are often visible
after just a minute. Many people believe that corrosion
is a slow process and the effects only become visible
after an extended period of time.
Where do the reaction partners come from?
Oxygen is ever present during any transport. The main source of water is condensation, which occurs when the temperature falls below the dew point.
Moisture in the package – in hygroscopic packaging materials or even hygroscopic packaged goods,
the air present in the sealed package and the air that later penetrates the packaging – plays an
important role in relation to temperature.
Moisture is present as water vapour. This is water in its gaseous state, i.e. as a true gas. It is not to
be confused with the steam you see rising from boiling water or in the form of clouds.
It is a basic law of physics that cold air cannot hold as much moisture as warm air. The table below
provides two examples:
• 1 m³ of air can hold 10.44 g of water vapour at 20°C
and a relative humidity of 60% (normal temperate conditions).
• 1 m³ of air can hold 45.99 g of water vapour at 40°C
and a relative humidity of 90% (tropical conditions).
This example shows that warmer air can hold more than four times as much water vapour as its cooler counterpart. As soon as the temperature falls below the dew point, the quantity of water vapour
that the air can no longer hold is released as condensed water.
If warm, humid air cools rapidly – so it can no longer hold the same amount of moisture – it will
release this moisture in the form of condensation (visible droplets) around so-called condensation
nuclei, e.g. dust particles. We have all observed this effect when we take a bottle out of the fridge.
We remove the cold bottle and take it into a warmer and more humid
atmosphere. Visible droplets of water immediately start to form on the
bottle. This is because the cold bottle cools the warm, moist air surrounding it. The air releases its moisture which we see as condensation on the
bottle’s surface. You will also recognise this effect if you wear glasses. In
winter, for example, they mist up instantly when you come into a warm,
humid room after a walk outside. Condensation continues to form on
them – even after they have been wiped – until their surface temperature
has reached equilibrium with that of the room, i.e. when they have acclimatised. The same principle applies to both the bottle and the glasses
A similar process also occurs inside export packaging. In fact, it can happen several times a day, e.g.
when night falls or the package is moved from a cold warehouse into the sunshine or the warm hull
of a ship. The sun’s rays warm the container which then cools at night etc. Packaged goods which
can store heat efficiently may take days, weeks or even months to acclimatise fully.
However, moisture can also reach packaged goods directly. Tropical rainstorms, for example, can be
very violent and are capable of flooding containers and packages. Spray, dripping water and rainwater can also penetrate containers, packages or barrier layers and thus provide one of the required
reaction partners.
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How much corrosion is already present before packaging?
Before we start looking for solutions, we first have to ask ourselves how much corrosion potential we seal into an export package and in what state. Quite often it is too late to implement the
preservation measures. The reactions may actually be inevitable already. As a result, the “sealed
in” reaction potential will be more powerful than the active agents used to protect the goods. The
following diagram shows a dividing line between production, packaging and subsequent transport
processes (transport, handling, storage). The time line runs from left to right.
On the surface, it would seem natural to suggest that we must seek out the risks and corrosion
potentials caused by the sometimes extreme conditions experienced during transport (primarily
climate, secondarily mechanical) and provide protection. That is largely correct. Extreme climates
with large fluctuations in temperature and humidity, environmental effects, gases, interactions,
salts, aggressive atmospheres, condensation, wetting, etc. pose significant problems. In short, a
whole host of known and unknown situations can arise at unknown times and in unknown strengths
or concentrations. The emphasis is on “can”. It is also perfectly possible for one journey to run completely smoothly while another to the same destination poses a whole series of challenges. Mother
Nature should not be underestimated.
PRODUCTION
Known
SHIPPING
Unknown
Look at the above diagram to the left of the central dividing line. As you can see – depending on
the product – there are quite a number of possible circumstances which could result in corrosion
reactions or favour such reactions in future. These include cleaning processes with aggressive baths
and residues from such treatments, lubricants and auxiliary materials, inclusions in metals, temporary preservation products, interactions, contaminants, rolling oils, cooling lubricants, corrosion
processes which have already begun (corrosion of internal mechanisms), etc. Looking to the left of
the central line, we can see that in tracing a product back through its production path we should
actually encounter a large number of known values and processes. This is in contrast to the transport route on the right.
However, the probability of an unknown factor influencing corrosion grows in proportion to the
complexity of the product and the size of its manufacturer. Autonomous sub-processes inevitably
become less transparent and the more we look at them in detail, the more possible faults and errors
we find. Depending on the number of parts and semi-finished products purchased from third-party
suppliers, it may even be impossible to make a clear, or indeed any, assessment of potential corrosion risks. The chances of guaranteeing consistent chemistries throughout the process – from individual stages of production to preservation for shipment – lie somewhere in the range between slim
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and non-existent. In other words, it is very probable that corrosion processes have already begun
by the time a product is being protected for shipment or that they are already inevitable. Difficult
conditions during transport can then trigger or accelerate these reactions. Consequently, export
packagers and shipping departments are confronted with problems they cannot identify, cannot be
aware of and cannot solve even using the best preservation techniques. Nevertheless, they are liable or can be held responsible for the resulting damage. Inexplicable, serious corrosion, which occurs
despite the use of the correct corrosion protection methods, is a clear indication of this type of
problem. And the task of securing evidence of the damage in a distant, foreign country is often difficult or no longer possible. Another preventive measure worth mentioning is corrosion protection by
design. Careful selection, arrangement and combination of materials and components can minimise
or even eliminate potential risks before the product has left the drawing board. This throws down a
challenge to designers: prevention is better than cure.
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What can we do to prevent corrosion?
In its simplest terms, the principle works as follows:
[A] removing one of the possible reaction partners, or
[B] keeping one of the possible reaction partners at a safe distance from the vulnerable positions.
If one of the reaction partners is missing, it is virtually impossible for the reaction to take place.
These are the two most common approaches to providing temporary corrosion protection in export
packaging. And they are the techniques we will now look at in more detail.
The following corrosion protection methods are widely used in export packaging:
• Desiccant method
• VCI method
• Protective coating method
For the sake of completeness, the following methods are also sometimes used:
• Inert gases
• Electromechanical drying
• Active cooling
• Bacterial phosphating etc
However, these techniques are so specific and used so rarely in our sector that we will focus here on
the first three methods.
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Preparation phases for temporary corrosion protection
Cleaning
Thorough cleaning of the goods being packaged – especially of their surfaces – is essential prior to
all temporary corrosion protection methods. Every particle of dirt and all contaminants, manufacturing residues and fingerprints must be removed. At the same time, you must take care that the
cleaning agents and methods do not themselves initiate any additional corrosion risks.
A wide selection of cleaning methods and agents are available but not the subject of this discussion.
We recommend that you discuss the appropriate cleaning procedures with the manufacturers and
designers of the goods.
Drying
Drying is very important. But clean, dry surfaces are only the beginning. Many plants and machines have tanks or reservoirs for liquid fuels, auxiliary and operating materials or coolants. If these
cannot be removed for transport, you must ensure that no solids, liquids or gases can escape from
them. You should also check for potentially hazardous materials. We recommend that you discuss
this with the designers because these types of containers are often difficult to identify.
You should also ensure that painted surfaces are dry and no excessively high solvent emissions are to
be expected.
Acclimatisation
Before starting the selected preservation method, check that the goods are properly acclimatised
to the ambient room or environmental conditions. The core and surface temperatures of the goods
being packaged should be in equilibrium with the temperature of their surroundings. Large temperature differences can cause serious problems after the goods have been packaged. The greatest of
these is condensation forming inside the barrier layer before the active agents can take effect.
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Desiccant method
The desiccant method is based on the approach of
[A] removing one of the possible reaction partners.
In this case, it is the water. To do this, you must construct a system comprising two principle components.
1st component.
A barrier layer which is – virtually – impermeable to water vapour and separates the packaged goods
from the external atmosphere. This barrier layer is usually made of a film which vacuum wraps and
hermetically seals in the contents. Two main types of film are used. These are
a) polyethylene film. For shorter preservation periods of max. 12 months..
b) aluminium composite films. These consist of three layers: aluminium to keep out water vapour, polyethylene as a sealing layer and polyester to reinforce the film for preservation periods of more than 12 months.
2nd component.
A medium which is capable of removing humidity (water vapour) from the atmosphere inside this
barrier layer. This process is known as adsorption, i.e. the substance binds in gases or other dissolved substances due to its surface structure and chemical properties. The medium is known as a
desiccant.
These two components – the film and the desiccant – work together to create a relatively dry, artificial micro-climate inside the barrier layer. Ideally, they should reduce the relative humidity to a
level below 40%. Experience has shown that condensation does not form below this level. The effect
is to remove one of the elements that can trigger or favour the process of corrosion.
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Desiccant
Desiccants can be made from a variety of substances. The most commonly used material in Europe is bentonite – a type of clay similar to cat litter. Other substances include zeolites (molecular
sieves) and silica gel. These have become less important in European export packaging over recent
years due to the environmental damage caused by the chemicals and their manufacturing processes.
However, they are still quite commonly used in the Far East. Desiccants are supplied as granules packaged in paper or textile bags, cartridges or other application-specific formats. Desiccant bags are
the most important form in our sector and supplied in two principal forms: low-dust and dust-proof.
The individual bags are themselves packaged in polyethylene bags (as a barrier layer) until they are
ready to be used. A strip of indicator paper is enclosed inside this barrier layer. This acts as a hygroscope and records the presence/absence of moisture – allowing the user to assess the humidity and
activity status of the desiccant before it is used. If the desiccant is active, the indicator paper will
be blue and the user knows that the humidity level inside the bag is less than 8%. If the paper turns
pink, the desiccant is no longer active. It is saturated with moisture and can no longer be used.
Blue indicator paper: Desiccant is active and can be used
Pink indicator paper: Desiccant is saturated and can no
longer be used.
Indicator paper in the packaging
of the desiccant bags.
All desiccants have the property of adsorbing water vapour very efficiently in their external and internal cellular surface structures. Under a microscope, a grain of desiccant would look like a natural
sponge, i.e. a form with internal structures (pores and channels) which give it an extremely large
internal surface area in relation to the size of the grain. If you could spread out and join up all of a
grain’s cell walls, each grain would have an area of several square metres.
Torn desiccant bag
with visible grains
Magnified view of the
surface structure
Desiccants are measured in units that reflect the substance’s ability to adsorb water vapour. The
properties and test specifications are standardised in accordance with DIN 55 473. One “desiccant
unit” must be capable of adsorbing at least 6g of water vapour at a temperature of 23(+/-2)°C/40%.
At the same time, its mass must not exceed 39 g and its volume must be no greater than 45 cm³.
Desiccant bags are available in a variety of pack sizes. The standard sizes are 1/6, 1/3, 1/2, 1, 2, 4,
8, 16, 32 and 80 units per bag. The 32-unit bag is the most commonly used in the export packaging
sector. It is also known as the “kilo bag” because it weighs around one kilogramme.
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Barrier layer film to exclude water vapour
The barrier layer film is usually a pre-fabricated hood welded into a box shape and made from the
appropriate type of film. All films are only approximately impermeable to water vapour. Water vapour is still capable of passing through the molecular structure of the film. This is known as diffusion
(penetration of a substance as a consequence of the thermal motion of its molecules and the diffusion equilibrium). In other words: technically, no film can provide a perfect seal.
Nevertheless, there are significant differences in the performance of the two most widely used
types of film. The water vapour permeability (WVP) of
• aluminium composite films (ALU) is less than 0.1 g of water vapour/m²/day
• polyethylene films (PE) with a thickness of 200my (0.2mm) is 0.4 g of water vapour /m²/day.
The water vapour permeability values depend directly on the external atmosphere. The values
stated above refer to a test climate of 20°C with a relative humidity of 85%. At a temperature of
38°C and relative humidity of 90% (tropical climate), the permeability value rises only slightly for
aluminium film. In contrast, the value for polyethylene film increases to 2.0 or even higher. In Arctic
climates, the water vapour permeability value rises as the temperature falls. It should also be noted
that polyethylene film is not generally stable to UV radiation and tends to weather more rapidly.
Exposure to light, very high and very low temperatures speed up the weathering process with the
result that water vapour permeability rises rapidly. These types of film are therefore only recommended for short-term preservation (up to 12 months).
As water vapour permeability is measured per day, we have to add in another important factor affecting temporary corrosion protection: the transport and storage period. The longer the period, the
greater the quantity of desiccant required. The relationship is linear.
Polyethylene film
Aluminium composite film
There are a number of different application-specific
barrier layer forms. The box hood with a separate
base sheet is the most commonly used form for packaging machinery and plant components.
Height
Width
Width +
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Length
Length +
Hygroscopic materials
Hygroscopically active packaging materials such as wood, paper, cardboard, and padding can be
sources of moisture inside the barrier layer and are another important factor to be considered.
But the packaged goods themselves, or parts of them, can also be hygroscopically active (to some
extent) and introduce water into the package. Naturally, these are in a hygroscopic equilibrium with
the air that surrounds them. In other words, the moist material in the package will release moisture
into the surrounding air until the moisture concentrations in the material and the air are in balance. When the atmosphere changes so does the level of moisture in the packaging materials or the
hygroscopic packaged goods. Additional desiccant must be added to take account of this moisture
potential. According to DIN 55 474, 80 desiccant units are required for every kg of hygroscopic material in the package. However, in practice, it is not easy to work out the actual mass of hygroscopically active material in the package – and this figure is required for the calculation. In many cases,
the mass is not yet known when the order and desiccant calculation are being prepared and difficult
to calculate during the packaging process. Weighing is not a practicable solution so the estimated
mass of the packaging materials is almost always an educated guess made on the spot. The result is
usually the use of too much or too little desiccant.
How to achieve the optimum effect
One very important aspect to consider when using this method is the placement and attachment of
the desiccant bags inside the barrier layer. Please note the following key points.
Wherever possible, do not allow the bags to be in contact with the surface of the packaged goods.
Use intermediate layers of material to separate the goods and the bags.
Convection currents (dry air is heavier than moist air) mean that humidity will be higher in the upper section of a package. As a result, you should also distribute the majority of the bags around the
top where possible. One third below, two thirds above. Ensure that the bags are surrounded by sufficient free space for them to function efficiently. Sometimes, during the vacuum packing process,
desiccant bags are known to have become shrink-wrapped in film – rather like a ham. This separates
them from the internal atmosphere of the package and prevents them from functioning. When you
hang up the bags, ensure that they cannot swing back and forth.
The bags must be attached and stowed quickly because they begin adsorbing water vapour as soon
as their protective packaging is opened. The time between opening the protective packaging of the
bags, removing the air from within the barrier layer and welding it shut should be no longer than 10
minutes. Remove as much air as possible from inside the barrier layer by suction.
Allow adequate time for the desiccant to take effect inside the package. For example, condensation
may form within the barrier layer if you immediately expose the package to extreme temperature fluctuations – even if it is perfectly sealed
and contains an adequate quantity of active desiccant. In other words, it
starts raining inside the barrier layer. The desiccant is unable to adsorb
the condensation quickly enough and the conditions are in place for corrosion to begin.
This photograph shows condensation on the inside of the barrier layer
– a sure sign that the system has failed completely.
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Many different factors and influences can be at work here (temperatures and humidities inside and
outside the barrier layer) so it is difficult to make reliable, generalised statements. However, experience has shown that a period of 24 hours is usually enough for the desiccant to take effect.
How to monitor effectiveness
For long-term preservation it is advisable to include humidity indicators in the packaging. These are
impregnated indicator papers attached inside a transparent window in the package so they are visible from outside. These windows are incorporated in the barrier layer film
and enable you to monitor the humidity level inside the package over an
extended period. If the colour of the indicator changes to pink, you know
that the desiccants are saturated and must be replaced. We recommend
installing transparent windows if you plan to leave the package unopened
for a period of 18 months or longer. When attaching the window it is vital
to ensure the maximum possible distance between the window and the
nearest desiccant bag. If an indicator paper is in direct contact with the
desiccant, it can lead to a false reading.
Window for monitoring desiccant activity.
How to calculate the correct quantity
The required quantity of desiccant can be calculated in several ways – and the results of these calculations can differ dramatically. We recommend the slightly more complex method described in DIN 55
474, partly because of the relatively high level of legal certainty if damage does occur. The formula
takes account of the
•
•
•
•
•
•
•
temperature and humidity during the packaging process because these have a major influence on the quantity of water vapour present in the package when it is sealed,
permissible final humidity level inside the barrier layer in relation to the amount of water that can be adsorbed per unit of desiccant
volume inside the barrier layer
surface of the barrier layer
mass of hygroscopic materials included in the package
water vapour permeability of the barrier layer film
transportation and storage period.
The result of this calculation tells us the number of desiccant units required. This figure is rounded
up to determine the number of bags.
Please note that the volume used in the calculation is the theoretical volume inside the barrier layer
based on the dimensions. This is not truly accurate as the packaged goods also have a volume which
is not considered in the calculation. When processing the package, the aim is to create the smallest
possible volume. This is usually achieved by the use of adhesive tape. The less air there is inside the
barrier layer, the less moisture it can contain and the lower the risk. However, it is not advisable to
reduce the volume in the calculation.
We offer a number of IT tools on our website to help you calculate the required quantity of desiccant
in accordance with DIN 55 474: www.jakob-schober.de
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Cost-effectiveness
To ensure optimum cost-effectiveness, it can be worth comparing the costs of two types of film
against the aspect of time – the major influencing factor. Generally, PE film is about half the cost of
ALU film but requires a lot more desiccant. In addition, we must remember that installing bags of
desiccant also creates costs. This provides interesting data for a comparison.
Here is an example:
Assuming a box hood barrier layer with the dimensions 400 x 200 x 200 cm, the costs are as follows:
• aluminium composite film, approx. EUR 65.00
• polyethylene film approx. EUR 35.60
Quantity of desiccant required in 32 unit bags:
Transport/storage time
(months) Polyethylene film Aluminium composite films
6
12 bags
4 bags
9
17 bags
5 bags
12
23 bags
7 bags
18
33 bags
9 bags
The simplified cost calculation taking into account the costs of the barrier layer, desiccant and installation is then as follows:
Transport/storage time
(months) Polyethylene film Aluminium composite films
6
60.00 EUR
73.00 EUR
9
70.00 EUR
75.00 EUR
12
82.00 EUR
79.00 EUR
18
102.00 EUR
83.00 EUR
This table clearly shows that the costs converge between approx. 10 and 12 months. It means that
if you are planning to preserve goods for a period of 10 months or longer, it is more cost-efficient
to use aluminium composite film which is almost twice as expensive as PE film. This is shown in the
chart on the right:
35
31
33
27
29
25
21
23
17
19
15
11
Time in Months
13
7
9
3
5
1
COST CURVE FROM 1 TO 36 MONTHS
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Advantages and disadvantages of the desiccant method
The advantages of this method:
• universal applicability
• no potential active agent reactions
• relatively high level of legal certainty (DIN)
• relatively controllable level of effectiveness
• no removal of preservation agent required.
The disadvantages:
• high level of care required in processing (tightness)
• time intensive
• material intensive
• preservation agent requires time to take effect
• complex calculations required for active agent and dosing (over-/under-dosing)
• hygroscopically active materials in the package must be taken into account/identified
• need for processing speed (must be performed quickly)
• rugged barrier layer required (must not be damaged).
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Practical application of the desiccant method
In the following section, we will guide you step-by-step through a typical, widely used and practical
application of the desiccant method
Preparation
First prepare the pallet or base and provide it with the mounting options required to fasten the packaged goods. In this example, we are drilling holes which will be used to bolt the packaged goods
to the base.
Cleaning
It is vital to ensure that the base area is thoroughly cleaned to remove any chips or other contaminants before proceeding.
The base area should be flat. Make sure that no nails or nail tips are projecting from the base. Also
check that there are no splinters.
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First layer of padding
Next insert the bolts into the base from below. For optimum stability, the bolts should pass through
the square timbers if possible.
Now lay down the first layer of padding – packaging foam or bubble wrap. This layer of padding
should be min. 5 mm thick and protect the barrier layer.
First seal
Now place rubber washers on the bolts to seal the barrier layer. Their internal diameter should be
identical to the diameter of the bolt. Their external diameter should be large enough that they can
encompass the plate supporting the packaged goods.
Base section of the barrier layer
Next place the base section of the later barrier layer on the base and push the bolts through carefully to ensure a perfect fit. Check that this base section of the barrier layer overlaps the base
enough that it can be welded to the box hood later. During all subsequent stages you must ensure
that this film is not damaged, e.g. by stepping on it, tools, during positioning of the packaged goods
or by contaminants.
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Second seal
Now position the upper rubber washers precisely – as you did previously with the padding film.
It is advisable to use a special sealant (e.g. Terrostat) or rubber adhesive between the washers and the film.
Padding
Seal
Adhesive
Film
This diagram shows a cross-section of the padding/seal/
barrier layer construction.
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Top layer of padding
Now add the top layer – a second layer of padding film. Align it precisely and penetrate it with the
bolts as described above.
Place the goods on the base
It is advisable to pad the lower corners and edges before placing the goods on the base for packaging. Corner cushions, sections of packing foam or bubble wrap are suitable.
Take special care when using adhesive strips. The adhesives can react with painted surfaces – especially if these are not yet completely hardened – and cause damage. It is also possible that it will be
impossible to remove the adhesive strips. This could also result in damage and compensation claims.
When you place the goods on the base, ensure that you do not damage the goods or the barrier
layer.
Take care that you do not damage the bolt threads.
22
Padding the goods
Once the goods are in position you can pad the upper corners and edges.
It is essential that you cover all sharp corners, edges and projecting parts with plenty of padding to
prevent them damaging the barrier layer.
Bolt the goods into position and pad them
Bolt the goods firmly to the base with washers and nuts.
23
Stow and pad the desiccant bags
Next pull a section of padding completely over the goods and align it correctly. You can use openings
in the goods to store the desiccant bags.
However, it is crucial to ensure that the desiccant bags are not in direct contact with the goods. If
necessary, insert a separating layer of film or padding film between the surface of the goods and the
desiccant bag.
Then wrap the goods in padding film.
24
Finish padding the goods
The padding film must be stuck firmly in position and secured to prevent it from slipping.
Ensure that the padding protects not only the goods but also the barrier layer against the goods and
the external packaging.
Stow the desiccant bags
From this point on you must work very quickly because the desiccant starts adsorbing moisture
immediately.
Ideally, the desiccant bags should be positioned in the upper section of the package. Ensure that
they are not in direct contact with the surface of the packaged goods. Fasten the bags securely so
they cannot slip out of position.
If you use adhesive strips you must ensure that this does not significantly reduce the surface area of
the bag. If you suspend the bags, ensure that they cannot swing or slip. This could cause the ties to
break and the bag to cause damage within the barrier layer.
Generally, a number of desiccant bags are packed in transparent PE film bags. These bags contain
indicator papers which show the degree of dryness or saturation. See yellow arrow.
A blue colour indicates that the desiccant is capable of adsorbing
water vapour and may be used.
A pink colour indicates that the desiccant is already saturated and must
not be used. The desiccant can become saturated if the film bag has been
damaged or already been opened and not closed again properly.
25
Cover with the film hood
In the next step, we will cover the packaged goods with the film hood. Here it is very important that
the film does not come into contact with the floor. Particles of sand, chips or abrasive areas could
damage and create leaks in the barrier layer.
Weld the hood
Now weld the hood together with the base section. Take special care with the corners – they are
not easy to weld. It may be necessary to weld them several times and cross-wise as you have to join
several layers of film.
Leave open a small slit approx. 15-20 cm in length.
26
Evacuate the air
Insert a suction tube into the open slit and carefully evacuate the air contained inside the barrier
layer. You can do this with an ordinary vacuum cleaner. Take great care to avoid folds forming in the
film as these can stretch over projecting parts and become damaged.
You should also ensure that the vacuum you create is not too great. Even a normal vacuum cleaner
can create a vacuum that not only destroys the film but crushes whole machines
Completing the weld
After evacuating the air, remove the suction tube from the slit and weld the slit shut. You must do
this quickly or air will flow back into the package.
27
Secure the hood
To minimise the volume of the barrier layer if air enters the package at a later stage, we recommend that you tape the film as closely and compactly to the packaged goods as possible. Adhesive
tape is a suitable solution for this task. Tape down any sections of the hood which could start overhanging later. These could rub against the outer packaging and damage the film.
Wait for the desiccant to act
Now allow adequate time for the desiccant to take effect inside the package.
Unfortunately there are no binding values to tell you how long to wait.
It is best to allow the finished package to stand for 24 hours before you add the outer packaging and
move it to a different environment where it may be subject to significantly different temperatures
and/or humidities.
28
VCI method
The
Volatile Corrosion Inhibitor - method is based on the approach of
[B] preventing one of the possible reaction partners coming into contact with the surface of the
packaged goods.
Volatile: English. From Latin, “vaporising rapidly or fleeting”.
Corrosion: English, already explained
Inhibitor: From Latin, “substance that prevents or restricts chemical processes”.
The method could also be described as follows: a vaporised active agent prevents corrosion reactions occurring. Here, too, we target the reaction partner water. To do this, we must construct a
system comprising at least two components:
• A barrier layer which is – virtually – air-tight and separates the packaged goods from the
external atmosphere.
• An active agent which distributes itself across the surface of the packaged goods and thus
prevents it coming into contact with water.
Mechanism
VCIs are polar organic and inorganic compounds which can contain several separate active agents
with different properties.
VCI active agents can be used in two ways:
• in the vapour phase: Due to their high vapour pressures, these active agents evaporate (sublimation) very easily. The saturation concentration (saturation vapour pressure) within a closed
atmosphere is approx. 3-4 mg pro m³, or 3-4 ppm (parts per million). Subjectively, that is very
little. They are applied using carrier media such as films, papers, cardboard packaging, foams,
fleeces, cartridges, tablets, emitters, etc.
• in contact: The active agents are applied directly to the surface, e.g. as powders, aqueous/alcoholic solutions or oils.
These two methods are not mutually exclusive and can be combined or supplemented depending on
the specific application – assuming that they have a consistent chemistry. Never use active agents
from different manufacturers as these may react with each other in unknown and unwanted ways.
Inhibitors (active agents) produce an interaction between the surface being protected and its surroundings
29
This diagram shows the mechanism of VCI active agents.
VCI donor
Depending on the product, these interactions can take place in
several ways. Firstly, the active agents are adsorbed (deposited)
on the surfaces as a monomolecular film. This makes the surfaces water-repellent (hydrophobic). In other words, the VCIs insert themselves between the metal surface and the surrounding
e.g. as cathodic
e.g. as anodic
corrosion
corrosion
air – thus preventing direct contact with water and the possibiliprotection
protection
ty of electrochemical reactions. This applies to both anodic and
with steel
with copper
cathodic reactions. Secondly, a number of active agents are also
capable of repairing damaged protective passive layers of metal
surfaces by oxidation. In addition, some VCIs can regulate the
pH value within a barrier layer and on metallic surfaces. This
neutralises acidic contaminants and stresses. The active agents are also water soluble. They can
therefore pass through existing films of moisture and interpose themselves on the metallic surfaces.
Active agents
There is a large range of VCIs to choose from. There are active agents designed for specific metals
and so-called multi-metal agents. They differ in terms of their concentrations with multi-products
usually having a lower concentration.
Chemistry has now advanced to a level where multi-metal VCIs offer reliable protection. There are
good, documented examples of them providing long-term preservation in the real world. In some cases, however, it can be advisable to conduct an impact assessment with the manufacturer or discuss
whether it is suitable for the specific application. This applies to a number of active agents, especially if they are being considered to protect cast iron, galvanised steel, magnesium or solder.
Depending on the packaged goods, it may be necessary to use a complete VCI system. This involves
a combined, targeted application of different active agents to specific areas, e.g. oil on untreated
surfaces, installation of emitters in electronic components, spray treatment of contacts and finally
a barrier layer of VCI film to isolate the packaged goods from the external atmosphere. Systems can
be purchased as kits. These are ready-to-use packs tailored for use with, e.g. a specific type of machine. They contain all the necessary active agents in the correct dosages, barrier layers, padding
and labelling materials as well as consumables and auxiliary materials.
Many people justifiably ask about potential health and environmental hazards when using VCI products. VCIs which do no longer contain nitrite are now available on the market. Most, however, do
contain nitrite compounds. According to information provided by the manufacturers, these are only
present in very low concentrations – far below those encountered in food products (pickling salts
used in cured meats etc.). We can assume that VCIs do not pose a health hazard and indeed this has
been documented by toxicological studies. Despite this, we recommend that you always wash your
hands after contact with the active agents in order to avoid ingesting them.
30
Application of the VCI method
When designing a VCI package, you must ensure that the barrier layer is as air-tight as possible.
Unlike the desiccant method, it need not be impermeable to water vapour. This also means that the
barrier layer does not have to be welded shut, which simplifies the process of closing the package
and saves costs. Usually it is adequate to nail, staple, wrap or stick down the barrier layer with adhesive strips. However, you must ensure that no chimney effect results. In order to replace escaped
VCI, most users use significantly more active agent than required. The excess store of active agent
and high vapour pressure then resaturates the atmosphere again automatically.
VCI packaging is normally used to preserve goods for a period of around 24 months. Please note
that, for longer storage periods, we recommend ensuring the barrier layer is truly air-tight.
One major advantage of this method is that it is simple to implement – especially because it offers
some room for imperfections when creating the atmosphere inside the barrier layer. You can also
use thinner films (<200 my). If the barrier layer is opened during transportation, this usually does
not adversely affect the packaged goods if it is resealed in a relatively air-tight way. Another advantage is that no removal of the preservation agent is required. Once the goods have been unpacked,
the invisible active agents will automatically evaporate from the surfaces over time.
How to calculate the correct quantity
The quantity of active agent required is actually very low. Almost all users choose to use much more
agent than necessary because it allows them to dispense with hermetically sealing the package.
Even so, they still use a very small amount compared with the volume to be protected. Calculate
the dosage in accordance with the manufacturer’s instructions. The quantities usually refer to the
volume inside the barrier layer and may differ depending on the type of application and carrier material. Manufacturers provide practical, easy-to-use tables for this purpose.
Advantages and disadvantages of the VCI method
The advantages of this method:
•
•
•
•
•
•
•
easy to process
easy to dose
the barrier layer need not comply with high standards
easy to close the barrier layer
barrier layer need not be impermeable to water vapour
large range of active agent application methods
no removal of preservation agent.
31
The disadvantages:
•
•
•
•
•
preservation agent requires time to take effect
potentially incompatible with certain surfaces
potentially ineffective with certain surfaces
knowledge required regarding the materials/surfaces to be protected
no way of monitoring or displaying the activity of the agent.
Practical application
We will now guide you step-by-step through three typical, practical applications in the following
three sub-categories:
• VCI barrier layer film impregnated with active agent
• Polyethylene barrier layer film with VCI bubble wrap impregnated with active agent
• Polyethylene barrier layer film with VCI foam impregnated with active agent
32
VCI barrier layer film impregnated with active agent
With this method, we will use a VCI film as the active agent carrier. The film is a coex polyethylene
film coated with a sublimating VCI on one side. A multilingual label on the film clearly identifies the
active side.
Its store of active agent is designed for a barrier layer volume of around 0.3 m³ per m² of film. If
this store is insufficient to protect the volume, you will have to enclose an additional and appropriate source of active agent in the package.
This could be:
•
•
•
•
•
VCI
VCI
VCI
VCI
VCI
foam
powder
tablets
emitters
paper
In this example, we will protect exposed, untreated parts using VCI paper and appropriate cavities
using VCI emitters.
You can also use a film coated with sublimating agents on both sides.
33
Preparation
First prepare the pallet or base and provide it with the mounting options required to fasten the packaged goods. In this example, we are drilling holes which will be used to bolt the packaged goods
to the base.
Cleaning
It is vital to ensure that the base area is thoroughly cleaned to remove any chips or other contaminants before proceeding. The base area should be flat. Make sure that no nails or nail tips are
projecting from the base. Also check that there are no splinters.
34
Base film
Next place the VCI base film on the base and align it correctly. Ensure that the clearly labelled side
containing the active agent is facing upwards.
Fasten the base film
Once it is aligned, push the bolts/screws carefully through the film.
Seal the bolts
We recommend that you seal the gap between the film and the bolts with a rubber seal. This also
prevents direct contact between the film and the packaged goods at the support points.
35
Place the goods on the base
It is advisable to pad the lower corners and edges before placing the goods on the base for packaging. Corner cushions, sections of packing foam or bubble wrap are suitable. These padding
materials can also contain VCIs.
Take special care when using adhesive strips. The adhesives can react with painted surfaces – especially if these are not yet completely hardened – and cause damage. It may even be impossible to
remove the adhesive strips after exposure to thermal effects. This could also result in damage and
compensation claims. When you place the goods on the base, ensure that you do not damage the
goods or the base film. Take care that you do not damage the bolt threads.
Pad the corners and edges
Once the goods are in position you can pad the upper corners and edges. It is essential that you cover all sharp corners, edges and projecting parts with plenty of padding to prevent them damaging
the barrier layer.
36
Additional active agent
You can provide additional protection for untreated and exposed parts at particular risk of corrosion
using VCI padding materials. In this example, it is VCI paper. Firstly, this provides padding and direct
VCI protection. Secondly, it is an additional source of active agent.
Padding
It is advisable to use padding materials to prevent direct contact between the packaged goods and
the barrier layer. This provides mechanical protection against vibration and motion for the barrier
layer. Secure the layer of padding to prevent it from slipping. In this case we are using bubble wrap.
If necessary, it can also contain active agent.
Cavities are useful places to stow VCI emitters so active agent penetrates the interior of the packaged goods.
37
Cover with the film hood
In the next step, we will cover the packaged goods with the VCI film hood. Here it is very important
that the film does not come into contact with the ground. Particles of sand, chips or abrasive areas
could damage and create leaks in the barrier layer.
Close the hood
You can close the barrier layer using nails or staples. Welding is not required as the package need
not be impermeable to water vapour.
Ensure that you make the package as air-tight as possible. You must prevent chimney effects arising.
In this example, the barrier layer hood is being nailed under nailing strips or stapled to the base
sheet. Depending on the application, you may be able to staple the films together and not require
the strips.
38
Secure the hood
To minimise the volume of the barrier layer if air enters the package at a later stage, we recommend that you tape the film as closely and compactly to the packaged goods as possible. Adhesive
tape is a suitable solution for this task. Tape down any sections of the hood which could start overhanging later. These could rub against the outer packaging and damage the film.
39
Wait for the VCI to act
Now allow adequate time for the VCI to take effect inside the package. As the various combinations
of active agent require different times to act, it is impossible to provide reliable time information
regarding this aspect. Experience has shown that a period of 16 to 24 hours is adequate.
40
Polyethylene barrier layer film with VCI bubble wrap impregnated with active agent
In this version, the barrier layer is a simple hood of polyethylene film. Use VCI bubble wrap here as
a source of active agent and padding material.
If the store of VCI in the padding film is insufficient to protect the volume, you will have to enclose
an additional and appropriate source of active agent in the package.
This could be:
•
•
•
•
•
VCI
VCI
VCI
VCI
VCI
foam
powder
tablets
emitters
paper
In this example, we will provide additional protection for exposed, untreated parts using VCI paper
and for appropriate cavities using VCI emitters. You can also spray the active agent onto these untreated parts.
41
Preparation
First prepare the pallet or base and provide it with the mounting options required to fasten the packaged goods. In this example, we are drilling holes which will be used to bolt the packaged goods
to the base.
Cleaning
It is vital to ensure that the base area is thoroughly cleaned to remove any chips or other contaminants before proceeding.
The base area should be flat. Make sure that no nails or nail tips are projecting from the base. Also
check that there are no splinters.
42
Base film
Next place the polyethylene base film on the base and align it correctly.
Fasten the base film
Once it is aligned, push the bolts/screws carefully through the film.
Seal the bolts
We recommend that you seal the gap between the film and the bolts with a rubber seal. This also
prevents direct contact between the film and the packaged goods at the support points.
43
Place the goods on the base
It is advisable to pad the lower corners and edges before placing the goods on the base for packaging. Corner cushions, sections of packing foam or bubble wrap are suitable. These padding
materials can also contain VCIs.
Take special care when using adhesive strips. The adhesives can react with painted surfaces – especially if these are not yet completely hardened – and cause damage. It may even be impossible to
remove the adhesive strips after exposure to thermal effects. This could also result in damage and
compensation claims.
When you place the goods on the base, ensure that you do not damage the goods or the base film.
Take care that you do not damage the bolt threads.
Pad the corners and edges
Once the goods are in position you can pad the upper corners and edges. It is essential that you cover all sharp corners, edges and projecting parts with plenty of padding to prevent them damaging
the barrier layer.
44
Additional active agent
You can provide additional protection for untreated and exposed parts at particular risk of corrosion
using VCI padding materials. In this example, it is VCI paper. Firstly, this provides padding and direct
VCI protection. Secondly, it is an additional source of active agent.
Padding
Padding with VCI bubble wrap. This material not only provides padding but also adds a concentrated
source of VCI to the barrier layer.
Furthermore, it has the additional advantage of providing effective insulation.
45
It is advisable to use padding materials to prevent direct contact between the packaged goods and
the barrier layer. This provides mechanical protection against vibration and motion for the barrier
layer. Secure the layer of padding to prevent it from slipping. In this example, it is VCI bubble wrap.
Cavities are useful places to stow VCI emitters so active agent penetrates the interior of the packaged goods.
Cover with the film hood
In the next step, we will cover the packaged goods with the film hood. Here it is very important that
the film does not come into contact with the ground. Particles of sand, chips or abrasive areas could
damage and create leaks in the barrier layer.
46
Close the hood
In the next step, we will cover the packaged goods with the film hood. Here it is very important that
the film does not come into contact with the ground. Particles of sand, chips or abrasive areas could
damage and create leaks in the barrier layer.
Secure the hood
To minimise the volume of the barrier layer if air enters the package at a later stage, we recommend that you tape the film as closely and compactly to the packaged goods as possible. Adhesive
tape is a suitable solution for this task. Tape down any sections of the hood which could start overhanging later. These could rub against the outer packaging and damage the film.
47
Wait for the VCI to act
Now allow adequate time for the VCI to take effect inside the package.
As the various combinations of active agent require different times to act, it is impossible to provide reliable time information regarding this aspect. Experience has shown that a period of 16 to 24
hours is adequate.
48
Polyethylene barrier layer film with VCI foam impregnated with active agent
In this version, the barrier layer is a simple hood of polyethylene film. Use VCI bubble wrap here as
a source of active agent and padding material.
If the store of VCI in the padding film is insufficient to protect the volume, you will have to enclose
an additional and appropriate source of active agent in the package.
This could be:
•
•
•
•
•
VCI
VCI
VCI
VCI
VCI
foam
powder
tablets
emitters
paper
In this example, we will protect exposed, untreated parts using VCI paper and appropriate cavities
using VCI emitters. You can also spray the active agent onto these untreated parts.
49
Preparation
First prepare the pallet or base and provide it with the mounting options required to fasten the packaged goods. In this example, we are drilling holes which will be used to bolt the packaged goods
to the base.
Cleaning
It is vital to ensure that the base area is thoroughly cleaned to remove any chips or other contaminants before proceeding.
The base area should be flat. Make sure that no nails or nail tips are projecting from the base. Also
check that there are no splinters.
50
Base film
Next place the polyethylene base film on the base and align it correctly.
Fasten the base film
Once it is aligned, push the bolts/screws carefully through the film.
Seal the bolts
We recommend that you seal the gap between the film and the bolts with a rubber seal. This also
prevents direct contact between the film and the packaged goods at the support points.
51
Place the goods on the base
It is advisable to pad the lower corners and edges before placing the goods on the base for packaging. Corner cushions, sections of packing foam or bubble wrap are suitable. These padding
materials can also contain VCIs.
Take special care when using adhesive strips. The adhesives can react with painted surfaces – especially if these are not yet completely hardened – and cause damage. It may even be impossible to
remove the adhesive strips after exposure to thermal effects. This could also result in damage and
compensation claims.
When you place the goods on the base, ensure that you do not damage the goods or the base film.
Take care that you do not damage the bolt threads.
Pad the corners and edges
Once the goods are in position you can pad the upper corners and edges. It is essential that you cover all sharp corners, edges and projecting parts with plenty of padding to prevent them damaging
the barrier layer.
52
Additional active agent
You can provide additional protection for untreated and exposed parts at particular risk of corrosion
using VCI padding materials. In this example, it is VCI paper. Firstly, this provides padding and direct
VCI protection. Secondly, it is an additional source of active agent.
Padding
It is advisable to use padding materials to prevent direct contact between the packaged goods and
the barrier layer. This provides mechanical protection against vibration and motion for the barrier
layer. Secure the layer of padding to prevent it from slipping. In this case we are using bubble wrap.
If necessary, it can also contain active agent.
Cavities are useful places to stow VCI emitters so active agent penetrates the interior of the packaged goods.
53
Insert VCI foam
A section of foam material can be used as a source of active agent. Avoid direct contact with
painted surfaces as these are not usually fully hardened at the time of packaging. In this example,
the foam section is placed on top of padding film in the upper area of the package and fastened in
position.
Cover with the film hood
In the next step, we will cover the packaged goods with the film hood. Here it is very important that
the film does not come into contact with the ground. Particles of sand, chips or abrasive areas could
damage and create leaks in the barrier layer.
54
Close the hood
You can close the barrier layer using nails or staples. Welding is not required as the package need
not be impermeable to water vapour.
Ensure that you make the package as air-tight as possible. You must prevent chimney effects arising.
In this example, the barrier layer hood is being nailed under nailing strips or stapled to the base
sheet. Depending on the application, you may be able to staple the films together and not require
the strips.
Secure the hood
Damit das Volumen der Sperrschicht durch evtl. später eindringende Luft so gering wie möglich To
minimise the volume of the barrier layer if air enters the package at a later stage, we recommend
that you tape the film as closely and compactly to the packaged goods as possible. Adhesive tape is
a suitable solution for this task. Tape down any sections of the hood which could start overhanging
later. These could rub against the outer packaging and damage the film.
In this example, please note that the active agent carrier is not separated from the space inside the
hood. This ensures that the active agents can evaporate and diffuse through the package.
55
Wait for the VCI to act
Now allow adequate time for the VCI to take effect inside the package.
As the various combinations of active agent require different times to act, it is impossible to provide reliable time information regarding this aspect. Experience has shown that a period of 16 to 24
hours is adequate.
56
Protective coating method
The protective coating method is also based on the approach of
b) preventing one of the possible reaction partners coming into contact with the surface
of the packaged goods.
This method is suitable for use with large and small areas, partial areas and individual components.
Application
The protective coating can be applied as a spray, with a brush or spatula, through immersion in a
bath, fusing or pouring. Depending on the material used, the coatings range from fluid to plastic to
firm to hard. The film thickness lies in the range between 5 and 500 my depending on the product
and application.
The coating acts as a barrier which prevents water and oxygen from reaching the vulnerable surface. Some media also contain inhibitors in order to prevent specific reactions. Other additives,
which aid creep behaviour, displace moisture or sweat (from hands), may also be included.
There is a large range of protective coating compounds to choose from. Almost every oil company
offers an extensive selection of products. They are generally categorised as containing solvents or
solvent-free. Protective coating media can be liquid, oily, paste-like or solid.
It is essential that you take the greatest care in preparing the surfaces. They must be as clean and
dry as possible. Dirt or acidic residues enclosed under a protective layer can cause serious damage.
In extreme cases, these contaminants can generate a specific micro-climate under the protective
coating, which promotes corrosion processes. In other words, it preserves the corrosion problem.
When selecting the protective coating medium, ensure that it is also suitable for use over a broad
temperature range (+80°C to - 60°C). Protective coatings have been known to liquefy in very warm
conditions or become porous or fragile at cold temperatures.
57
Advantages and disadvantages of the protective coating method
The advantages of this method:
• reliable protection
• no barrier layer required
• quick application.
The disadvantages:
• removal of preservation agent required (most protective coatings have to be removed)
• emissions due to solvents
• high standards of cleanliness required during application
• temperature sensitive.
58
Important: Wait before unpacking
Acclimatise before unpacking !!!
With all three methods, it is absolutely critical that you allow the package and its contents to acclimatise to the ambient conditions before unpacking them. Failure to do so may result in damage at
the final hurdle – despite effective corrosion protection. Packages with the potential to store large
quantities of heat or cold are at particular risk.
Here is an example: A four tonne freewheel was correctly preserved using the desiccant method
and stored in an unheated hall. In December, the company received an order for this freewheel
from Korea and it was immediately transported there by air cargo. It arrived two days later and was
unpacked immediately. As the change in climate was extreme (from cold and dry to hot and humid)
and took place over a very short period, the steel component still had a very low core and surface
temperature. Inevitably, the “refrigerator effect” was observed after the barrier layer was opened.
The component was completely covered with condensation within seconds. It was impossible to dry
the shipment because the condensation reformed instantly.
In other words: just as you need to give the active agent time to act when packaging the goods, you
must also allow the packaged goods time to adjust to the external climate before unpacking them.
Intense and rapid warming or cooling can lead to the formation of condensation, which can then
lead to corrosion. Please remember that acclimatisation can last days, weeks or even months. We
recommend that you attach multi-lingual labels to the barrier layer advising customers of the need
for acclimatisation. It is never a mistake to record the temperature and humidity at the time of
shipping. This can be important evidence if damage occurs.
These containers arrived in port
coated in ice several centimetres thick.
It has literally rained in this container.
The whole interior is wet.
Large droplets of water
are hanging on the ceiling.
59
Jakob Schober GmbH
Industriestr. 47 · D-69190 Walldorf · Fon +49 (0) 62 27 / 83 99 - 0 · Fax +49 (0) 62 27 / 83 99 - 11
[email protected] · www.jakob-schober.de