Letter 27057

Thin Dense Chrome Plate vs Chrome Plate  

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Please explain the difference between two platings - Thin Dense Chrome and standard Chrome Plate. Some platers do one but not the other. Both say the same Mil spec applies. AMS-QQ-C-320 [link is to spec at TechStreet]. The standard chrome plater I deal with says he can plate standard chrome plate .0002. Are there limits to how thick "Thin Dense Chrome" can be?

Is there a limit of how thin standard "Chrome Plate" can be? One plater told me that there are chemical differences between the two and the application is what determines the difference - if so, what are the criteria for each?

Thank You in advance for as much input as possible.

Nancy Boice
Purchasing Dept - Elmira, New York

Nancy,

AMS-QQ-C-320 is a standard for hard chrome and this standard include also a flash chrome who is about 0,0002 inch this can be plated from a regular chrome solution but if you need a thicker chrome deposit so must this be chrome plated in a chrome solution who works in a higher temperature and also different additive than a regular chrome solution contents.

Regards

Anders Sundman     surface finishing engineer Sweden

Difference between regular chrome and Thin Dense Chrome goes beyond what Specifications cover. It is related to chemistry, current density, temperature, etc. The deposit is also different regarding physical and mechanical properties, the later being basically harder and without cracks. It is, to my knowledge, a proprietary modification of a regular chrome bath.

Guillermo Marrufo
Monterrey, NL, Mexico

I agree with the comments made by Mr. Marrufo: thin dense certainly has different characteristics. However, there seems to be a lack of support by platers as to a standard for this plating. It would seem that AMS 2436^^AMS2438C should eliminate discussion although acceptance seems lacking. AMS 2460^^AMS2406 is the replacement for AMS QQ-C-320, yet when I specify Class 1, Type I, .0001 thick with a nickel underplate I get nothing but "no bids." The parts I'm plating are steel and the prospect platers will only plate directly on the steel (regardless of the spec). Does anyone plate Class 1, Type I, and what is the proper standard to ensure I get thin dense and not just decorate bumper chrome?

Dan Drummond
- Ann Arbor, Michigan

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Ed. note: "AMS 2436" appears to be a typo, Dan, as that is a spec for "Coating, Aluminum Oxide Detonation Deposition".

Yes, these numbers are both incorrect and I'm not sure how that happened. AMS 2438C (Plating, Chromium, Thin, Hard, Dense Deposit) is a definitive specification for thin dense chrome. The replacement for AMS-QQ-C-320 is AMS 2460 (Plating, Chromium) and seems more acceptable to platers as it doesn't carry the testing requirements defined in AMS 2438C.

Dan Drummond
- Ann Arbor, Michigan