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parts2clean-Forum 2016
Temporary corrosion protection in the process
chain
What options are available after cleaning?
Kerstin Zübert, application engineering / Hermann Bantleon GmbH
parts2clean-Forum 2016
Temporary corrosion protection in the process chain
What options are available after cleaning?
contents
general information on corrosion/corrosion protection
process chain „oily“
process chain „aqueous“
process chain „oily/aqueous“ respectively „aqueous/oily“
packaging after cleaning process = VCI
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General information on Corrosion / Corrosion Protection
What´s corrosion?
corrosion = lat. corrodere = „to gnaw away“
„to erode“
according to DIN EN ISO 8044 (formerly DIN 50900):
Reaction of metallic material with its surroundings, which causes a
measureable change of the material and could lead to impairment of the
metallic component or a complete system.
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General information on Corrosion / Corrosion Protection
Corrosion describes a well-known process in everyday life that occurs mainly on
the metal surface.
Everybody already has seen rust damage at an automobile or metallic utensils.
By general corrosion a big part of the technical metals, produced with great
efford, changes from elemental again in the connection state.
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General information on Corrosion / Corrosion Protection
reasons for corrosion:
Corrosive atmosphere in the surroundings
Pollutant content (e.g. sulfurdioxide, „sea air“)
Moisture content (corrosion stats at app. 55% rel. humidity)
Formation of a galvanic cell
Current flow between two metals in the presence of a electrolyte
Liquid or gasiform corrosive mediums
e.g. acids
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General information on Corrosion / Corrosion Protection
In the electrochemical corrosion the corrosion processes take place on the
metal surface in an electrically conductive water layer, called electrolyte.
As electrolyte even an extremely thin humidity film or water remainder in a
gap, but also, hand welding sweat stains on workpieces („finger prints“)
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General information on Corrosion / Corrosion Protection
Electrochemical oxygen corrosion of wet steel surface
(water drop on the metal surface)
Quelle: www.schulestudium.de/Chemie/Reaktionsgleichung_Rosten-Eisen.html
Schematic exposition: rusting of iron in the presence of water and oxygen
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General information on Corrosion / Corrosion Protection
Corrosion protection
The various manifestations and mechanisms of corrosion require a
targeted use of the many available anti-corrosion measures and
methods.
They are essentially aimed to reduce the speed of the respective
corrosion process on a non-critical level, thereby ensuring an adequate
technical service life of the respective product
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General information on Corrosion / Corrosion Protection
The protective measures can be divide appropriate to time and place
of their engagement in a corrosion system:
a)
b)
c)
d)
Construction and material-related measures
Separation of medium and to protect object by coatings (passive
corrosion protection - in the field of corrosion protection media, however
temporarily)
Changes of the attack medium
Electrochemical interventions in the corrosion reaction itself
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Process chain „ oily“
Cutting
process
with oil
Cleaning
with solvent
cleaners
Oily
corrosion
protection
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Process chain „oily“
Process chain at the customer
Machining with cutting oil
Components after processing in goods carriers
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Process chain „oily“
Process chain at the customer
Cleaning with solvent cleaner
Applying oily corrosion protection (relubrication)
Packaging with VCI
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Process chain „oily“
Advantages / Disadvantages oily corrosion protection
advantages
disadvantages
Compared with aqueous products
significantly longer corrosion protection
times are possible
VDA 19: by oil film particles can adhere to
the surface
VCI-packaging is not necessary
Assembly / processing:
might need to be cleaned again
OEM approvals often available only for oily
products, for example, DBL, VW QP, etc.
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Process chain „aqueous“
Cutting
process with
emulsions
Cleaning
with aqueous
cleaners
Water-based
corrosion
protection
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Process chain „aqueous“
Mode of action of aqueous corrosion protection
Aqueous
corrosion
protection
Film formers
< 1 µm
hydrophobic
films
Amincontaining
products
Film formers
> 1 µm
Oil/wateremulsions
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Process chain „aqueous“
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Process chain „aqueous“
Process chain 1
• machining with emulsion
• aqueous cleaning (set pieces)
• packaging (partly with VCI)
according to customer
specifications
Process chain 2
• grinding with emulsions
• aqueous cleaning (bulk)
• applying oily corrosion protection
(emulsion)
• delivery to customers
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Process chain „aqueous“
Advantages / Disadvantages of aqueous corrosion protection
advantages
disadvantages
Further processing without problems Usually only short-term protection
- no cleaning before assembly
against corrosion possible - longer
required
periods of protection only possible in
combination with VCI packaging
VDA 19: no problems with adhering
particles
corrosion protection is lost quickly by
condensation
cleaner = corrosion protection
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Process chain „oily/aqueous“ respectively „aqueous/oily“
process chain „oily/aqueous“
Cutting
process
with oil
Cleaning
with
aqueous
cleaners
Aqueous
corrosion
protection
process chain „aqueous/oily“
Cutting process
with emulsions
cleaning/corrosion
protection
solvent based
DW-products
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Process chain „oily/aqueous“ respectively „aqueous/oily“
process chain „oily/aqueous“
process chain „aqueous/oily“
By oil entry in aqueous cleaners
stronger bath contamination
Use of Dewatering products
• Main task corrosion protection
• Also cleaning effect
Cleaning of oil by aqueous
cleaners sometimes difficult =
residues poorer wetting by
corrosion = corrosion !!!
Monitoring of the baths is
necessary = draining the water
phase and filling with fresh product
(depending on the application –
eventually several times a day)
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Process chain „oily/aqueous“ respectively „aqueous/oily“
Oily cutting = turning machine
aqueous machining = Vibratory finishing
aqueous cleaning
dipping in DW-fluid / cleaning
with chlorinated hydrocarbon/hydrocarbon
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Packaging after cleaning = VCI
By the coating-method, we separate the corrosion enabled metal from the
attacking atmosphere by applying an oily/waxy layer on the surface.
The VCI method works by emitting of corrosion inhibitors and forming of
protective adsorption film in closed packaging.
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Packaging after cleaning = VCI
What means VCI?
The acronym VCI stand for Vapour /Vapour phase Corrosion Inhibitor
This term refers to substances transported via the gas phase and build
up a corrosion protection on the metal surface.
VCI describes an active principle!!!
The composition of the active substances and the associated corrosion
protection effect of different products differ.
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Packaging after cleaning = VCI
Mode of action in detail
1)
2)
3)
VCI-active component evaporate (sublimate) from the carriers material
into the closed package space.
VCI-active components mixed by diffusion into the packaging space,
concentrates in them (construction phase) and begin to adsorb on the
metal surface
Forming an monomolecular VCI-film on the metal surface
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Packaging after cleaning = VCI
Note:
Parts must be completely dry and be cooled before packing!!!
(rule of thumb = component temperature max. 10 ° C above ambient temperatur)
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Temporary corrosion protection in the process chain
What options are available after cleaning?
Questions???
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