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Q. We are currently on a refinery project in the South east and one of our scope is to supply and install cold supports. Our bolts and nuts are required to have a finish of bright zinc plated passivated to class 2d as per BS1706 spec. We have been offered a passivation class 2C. Due to lack of reliable literatures we would like to ask your opinion if the deviation from 2D to 2C are of tolerable property. Our latest lab test report in Singapore approves 25 micron plating thickness for class 2d. any info on 2c?

Will appreciate very much,


Ver Chavez


RFQ: I have 60 pieces of outdoor equipment rack, sizes: 1000 w x 900 d x 2000 h. The cabinet is made of 3 mm mild steel sheet with compliance to EN10025 and BS729.

The coating is electroplated zinc passivated to BS1706 class B Zn 3 and an anti-graffiti two-pack polyurethane finish.

The working location is south China.

Best regards,



Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)

Q. Dear ladies/sirs,

I need badly to know the standard of BS1706-FE-ZN5.

Who can tell me?

Thank you very much!

Best regards,

Will Wang


A. Hi Will. This is a specification for a minimum thickness of 5 microns of zinc on a ferrous substrate. My understanding from previous postings on this site is that BS-1706 was superseded by BS EN 12329, itself later superseded by BS EN ISO 2081:2008. You should probably get a copy of that spec and ask your customer to change the spec to the current one. Good luck.

Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey
May 2013

Q. Could you explain to me about Fe/Zn 8c2C per ISO 2081 and ISO4520 amx THK 20 microns.


Tawatchai Sujitranuruk


thumbs up sign Thank you for your several recent helpful responses to other people's questions, Tawatchai. Do you wish to order these two ISO specs, but need to know from where?

Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

Q. Thank you Mr. Mooney for your call back. This specs above my customer requires. Could you introduce me for the name of electro plating standard hand book? Because I want to know the matter inside such as: ISO_ _ _ for Cr plating maker must do Ni plate how many micron, Cr plate how many micron, how much time for salt spray test, etc.

Best regard,

Tawatchai Sujitranuruk


A. Hi again. I think I understand. The way this works is there are a number of standards writing bodies (ISO is one of them), and there are individual specifications for different types of plating (for example, ISO 2081:2088 is a spec for zinc plating). Then that spec may offer options such as different thicknesses of zinc plating and different types/colors of chromate conversion coatings. If you look at a copy of ISO 2081:2008 you will understand the idea. Good luck.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

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Q. In the UK "BS EN ISO 2081" is used for specifying "electroplated coatings of zinc with supplementary treatments on iron or steel". However in this standard there is no mention of thick-film / full or thin-film passivation. There is also no mention of trivalent or hexavalent versions of the chromate conversion coatings.

Does anyone know how to specify these properties? Is there another standard that I am not aware of?

Tim Douglas

October 5, 2010

A. Hi, Tim. Half of your question will be easy to answer. You simply add the requirement of RoHS-compliant trivalent chromate to your referenced spec. "... in accordance with BS EN ISO 2081 except that chromate conversion coating must be RoHS-compliant trivalent coating."

The other half of your question, thick-film vs. thin-film, is more difficult because as far as I know there is no standard covering that yet. Modern trivalent chromates are still highly proprietary. You can specify a brand and process name, but that can severely limit the number of plating shops available to you.


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey
October 2010

Q. Having both standards for same component to be plated, one is BS EN ISO 2081 Fe/Zn25/D & another is BS EN ISO 12329;2000 Fe/Zn25/D. are both the same or any differentiation in it?

rohit patil

February 13, 2019

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