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March 16, 2016
To whom it may concern
General information on corrosion protection of Hilti installation systems
Dear customer,
Hilti is providing modular bolted installation systems and pipe rings with different materials and
corrosion protection systems. This letter is summarizing the state of the art known to Hilti on
corrosion of zinc coated steel structures (like the Hilti MQ, MQ-F or MI system and corresponding
pipe ring lines).
Lifetime of all zinc-coatings in undamaged state and under purely atmospheric corrosion attack can
be assessed based on coating specification (minimum thickness of zinc layer) and case-specific
average yearly zinc-loss rate.
The coating thickness is given by the product specification – but as corrosivity is depending on
local conditions, the customer needs to conduct an own assessment of corrosivity in the location of
installation.
The most accurate procedure to define the zinc-loss rate is an exposure test in the planned
location and situation (according to ISO 9226), lasting min. 1 year (which makes this approach
often not feasible due to timing constraints).
With bigger uncertainty, lifetime can be estimated through assessing corrosivity of the environment
in the actual application situation and using typical zinc loss rates (both defined in ISO standards).
For environmental conditions classified as C1 to CX according to ISO 9223:2012, the range of
average yearly zinc loss is defined in ISO 9224:2012, also stating that those values have a high
uncertainty level (please refer to this standard for details). This standard also shows figures that
the yearly zinc loss rate is decreasing over time, and shows for example loss values for the first
year, as an average for the first 10 years as well as the first 30 years of exposure.
Please see appendix 2 for further information on how to assess corrosivity according to ISO
standards.
Hilti Corporation
9494 Schaan
Liechtenstein
Feldkircherstrasse 100 I P.O. Box 333
T +423-234 2111 I F +423-234 3332
www.hilti.com
Rechtsform: Aktiengesellschaft I Sitz: 9494 Schaan
ÖR-Nr.: FL-1.011.557-0 I MWST-Nr.: 50 555
Under those assumptions, a calculated lifetime range in dependency of the zinc thickness can be
derived:
Category according
ISO 9223:2012
C1
C2
C3
C4
C5
CX
Resulting estimated lifetime range in years (based on ISO 9224:2012)
5 µm zinc
13-20 µm
45 µm zinc
70 µm zinc
zinc
>100*
>260*
>900*
>1400*
10 – 100**
32 – 260*
110 – 900*
175 – 1400*
2 – 10***
9 – 32**
40 – 110*
63 – 175*
1 - 3***
3 – 11***
16 – 40**
31 – 63*
<1***
1 – 4***
5 – 16***
12 – 31**
<1***
<1***
2 – 5***
3 – 12***
* Lower end of range based on ISO 9224:2012, informative annex B, „Average corrosion rate during the first 30 years”
** Lower end of range based on ISO 9224:2012, informative annex B, „Average corrosion rate during the first 10 years”
*** Lower end of range based on ISO 9224:2012, informative annex A, Maximum corrosion attack/ 1 year exposure
Case-specific appropriate measures need to be taken in order to assure that the coating is in
undamaged state after installation as mentioned above. Some typical actions to achieve this are:
-
Cleaning after channel cutting
Cutting chips removal
Overcoating of uncoated areas (such as channel cut ends, relevant scratches, …)
(recommended coating see appendix 1)
The customer needs to assure that the environment only exposes the installed products to
atmospheric corrosion during its whole lifetime. The following list shows some frequent influencing
factors potentially strongly impacting above mentioned lifetime estimations:
-
Direct contact to other metals (e.g. stainless steel, copper, uncoated steel) - exception:
base material fasteners (e.g. anchors) being more noble than fastened parts
Stagnant water and/ or permanent humidity
Direct contact to soil
Exposure to corrosive substances or gases
Accumulation of corrosive deposits in non-weathered/ non-washed situations
The following maintenance instructions need to be followed in order to achieve and potentially
extend the lifetime of the installed structures:
-
Cleaning of structure if dusty
Yearly inspection of coating, checking for coating damages or spots of red rust
Repair of damages/ red rust spots (coating instructions see appendix 1) as soon as noticed
Replacement of parts with bigger areas of red rust not limited to smaller spots, but already
spreading on the surface of the part) as soon as noticed
Hilti Corporation
9494 Schaan
Liechtenstein
Feldkircherstrasse 100 I P.O. Box 333
T +423-234 2111 I F +423-234 3332
www.hilti.com
Rechtsform: Aktiengesellschaft I Sitz: 9494 Schaan
ÖR-Nr.: FL-1.011.557-0 I MWST-Nr.: 50 555
This product information is summarizing information contained in ISO standards and is neither a Hilti warranty statement
nor a lifetime guarantee. Further claims are explicitly excluded, unless mandatory national rules prohibit such exclusion.
In particular, Hilti is not liable for further direct, indirect, incidental or consequential damages, losses or expenses in
connection with, or by reason of the use of or inability to use the Product for any purpose unless provided by mandatory
applicable laws. Hilti is also not liable for loss or damage due to Customer’s incorrect assessment of the environmental
parameters (including corrosion parameters) at the location where the Products are used. This responsibility rests solely
with Customer and/or its subcontractors.
This product information shall be governed by and construed in accordance with the laws of (MO country).
Hilti Corporation
9494 Schaan
Liechtenstein
Feldkircherstrasse 100 I P.O. Box 333
T +423-234 2111 I F +423-234 3332
www.hilti.com
Rechtsform: Aktiengesellschaft I Sitz: 9494 Schaan
ÖR-Nr.: FL-1.011.557-0 I MWST-Nr.: 50 555
Appendix 1: Repair system
We give the following recommendations for the treatment of the cut edges on HDG channels.
ISO 1461, Chapter 6.3 states that
“Renovation shall be by thermal zinc spraying (for example ISO 2063) or by a suitable zinc-rich
paint where the zinc dust pigment conforms to ISO 3549 within the practical limits of such systems,
or by suitable zincflake or zinc-paste products. The use of a zinc alloy stick is also possible (see
Annex C)”
The same standard requests that “The treatment shall include the removal of any scale, cleaning
and any necessary pretreatment to ensure adhesion.”
Independent from the selection of the suitable repair coating we recommend applying at least two
layers to achieve a good protection against corrosion. The coating thickness on the patched area
shall be at least 100microns according to ISO 1461, Chapter 6.3.
As some of the above-mentioned coating types are not user-friendly or applicable on jobsites, Hilti
recommends our
Hilti Zinc Spray MZN-400 (Item No. 2048192)
for the repair of cut edges and smaller damages (e.g. spots of red rust) on hot-dip galvanized
parts.
The product-specific requirements data sheet must be observed for the application.
Hilti maintains warranty for their products under the condition of a correctly executed corrosion
protection with MZN-400.
The customer is responsible for the proper application and compliance with the guidelines and
standards of corrosion protection (as described above) as well as the Hilti Instructions for Use and
the Safety Data Sheets.
Hilti Corporation
9494 Schaan
Liechtenstein
Feldkircherstrasse 100 I P.O. Box 333
T +423-234 2111 I F +423-234 3332
www.hilti.com
Rechtsform: Aktiengesellschaft I Sitz: 9494 Schaan
ÖR-Nr.: FL-1.011.557-0 I MWST-Nr.: 50 555
Appendix 2: Assessment of corrosivity
Lifetime of zinc-coated systems is depending on the local corrosivity, which has to be assessed
and defined by the customer. ISO 9223:2012 is describing corrosivity categories C1 to CX for
atmospheric corrosion.
According to ISO 9226, C-classes are assessed based on experimental weathering tests on
standardized specimen.
Corrosivity can also be estimated – with bigger uncertainty - based on ISO 9223:2012 which is
defining a formula allowing to define the C-class based on local atmospheric conditions
(characteristic values: chloride dry deposition, SO2 dry deposition, temperature and relative
humidity).
The informative annexes of ISO 9224:2012 are defining the corrosion rates for the first year, as
well as for the first 10 and first 30 years of exposure, again mentioning a high uncertainty level of
this approach.
Due to the corrosion protection mechanism, optical appearance of zinc-coatings changes within its
lifetime. So called white rust and brown rust are corrosion products of the coating itself and indicate
an active sacrificial corrosion protection by the coating and are not critical. Small red rust spots
need local repair, but do not indicate end of lifetime of the whole coating.
In general, the end of lifetime for the zinc-coatings used by Hilti is reached when red rust is starting
to spread on the surface of the products, leading to corrosion of the steel structure not protected by
the coating any more. After this point in time, integrity and stability of the whole structure may still
be given, but is at risk. In order to exclude any risk for life and limb, it is strictly recommended to
further check integrity of the structure by qualified engineers without undue delay after aforesaid
occurrence of red rust.
The products need to be handled, installed and used correctly according to the applicable Hilti
Instruction For Use and within the application limits specified in the Hilti Technical Data Sheets, the
technical specifications and supporting product literature, and the relevant application limits shall
not be exceeded at any time; Lifetime of the products can highly be reduced when subjected to
other unforeseen external factors such as exposure to extreme forces or environmental conditions.
Please contact Hilti in any case of doubts or concerns.
Hilti Corporation
9494 Schaan
Liechtenstein
Feldkircherstrasse 100 I P.O. Box 333
T +423-234 2111 I F +423-234 3332
www.hilti.com
Rechtsform: Aktiengesellschaft I Sitz: 9494 Schaan
ÖR-Nr.: FL-1.011.557-0 I MWST-Nr.: 50 555