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topic 56433

"Commercial zinc plating" vs ASTM B633 standard

December 30, 2010

Q. Good Day,

I have been looking for information in regards to Commercial zinc plating vs zinc plating to the ASTM B633 [affil. link to spec at Techstreet] standard but unable to locate any info for the Commercial zinc.
I doubt that the commercial zinc can withstand any type of salt fog test correct?
If carbon steel parts are plated with the commercial zinc plating then what would be the plating thickness?
Any feedback would help.
Thank you.


Mario Callejas
Q.A. - San Carlos California USA

January 3, 2011

A. Hi, Mario. Although some plating shop managers say that "commercial zinc plating" is .0002" thick, I've heard others claim it is .00015", and still others claim that it is only "complete coverage". In my opinion the term is meaningless, a nice sounding term that sort of implies a fitness to purpose without having to actually promise it. It probably actually means "you can't reject it if it isn't rusted when you receive it"  :-)

I welcome other comments on the subject, but actually I think we should retire the term from our lexicon. Good luck.


Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha

September 25, 2019 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. A hardware and fastener supplier is telling me that commercial zinc plated fasteners have 3 microns of zinc and this is standard across the industry. Our company has always had 5 microns of zinc on the print.
Our Supplier has asked us to sign numerous deviations of fasteners or else require every fastener to be sent to outside plating process to get plated to 5 microns minimum.

There is not much difference between 3 microns and 5 microns for corrosion resistance, but I'm concerned that maybe the supplier simply doesn't want to be responsible for poorly plated fasteners.

I am considering simply going to all stainless and avoiding zinc fasteners altogether except for heavy bolts.

Is my supplier right about commercial zinc on fasteners? Should I be switching to stainless (I have galvanic concerns)? How does the automotive industry avoid corrosion of hardware for small hardware #4 thru #10?

Cameron Schmid
- Chicago, Illinois

September 2019

A. Hi Cameron. Yes, some people may feel that "Commercial thickness" is about 3 microns (or 0.00012"), but the term is actually unenforceable and meaningless. I understand that asking for a greater thickness than most plating shops are willing to do, and asking for it cheap, is a problem. Further, just because ASTM B633 [affil. link to spec at Techstreet] starts at 5 microns doesn't mean 3 microns is totally unacceptable for anything ever. Although personally I believe in quality and in specs, I also acknowledge that the majority of zinc barrel plating shops I visited over my career plated less than 5 microns.

I think the right resolution, if the vendor says his "Commercial" zinc plating is 3 microns, and you think it's enough, is for you to specify 3 micron thickness rather than "Commercial" thickness. As for the automotive industry, however, I don't believe they accept less than 5 microns -- I'd be happy to hear from anyone claiming the contrary. Good luck.


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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading

August 20, 2020

Ed. note:
abstract questions

Q. What is the thickness standard of Zinc plating on sheet metal parts?
Appreciate if you please tell me the standards of zinc plating metal sheet parts tests --

1) water resistance test hours?
2) Salt Spray Test hours?
3) other important tests if you recommend?

Anique Akram
- Lahore Pakistan

August 2020

A. Hi Anique. There is no one 'standard thickness'. ASTM B633 [affil. link to spec at Techstreet] starts at 5 microns for 'mild' service. Most automotive specs seem to be for 8 microns, which corresponds with 'moderate' service. 12-13 microns is sometimes specified for 'severe' service, and the spec goes all the way to 25 microns, although that's rarely spec'd and done.

I don't think your questions can be answered in a paragraph or two (just as an example, salt spray hours depend far more on the chromating than on the zinc thickness), but I think obtaining and studying that spec will put you well on the way towards understanding the issues of thickness, corrosion testing, and other tests.

Luck & Regards,

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Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading

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