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Thin Dense Chrome Plate vs Chrome Plate
Hard Chrome |
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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 BoicePurchasing Dept - Elmira, New York
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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
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Anders Sundman surface finishing engineer Sweden |
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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 MarrufoMonterrey, NL, Mexico
May 11, 2009
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^AMS2438 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?
- 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".
May 18, 2009
Yes, these numbers are both incorrect and I'm not sure how that happened. AMS2438 [link is to spec at TechStreet] (Plating, Chromium, Thin, Hard, Dense Deposit) is a definitive specification for thin dense chrome. The replacement for AMS-QQ-C-320 is AMS2460 [link is to spec at TechStreet] (Plating, Chromium) and seems more acceptable to platers as it doesn't carry the testing requirements defined in AMS 2438.
Dan Drummond- Ann Arbor, Michigan
May 19, 2011
Does a layer of 5-7 microns(0.0002") of thin dense chrome can be a better alternative to a layer of 20-25 microns (0.001") of hard chrome plating in terms of wear resistance, lubricity and component life ?
Jignesh PanchalPlating shop owner - India
May 19, 2011
Hi, Jignesh. I would certainly tend to doubt that a TDC coating could outlast a regular chrome plating 4X as thick, but I can't claim to know for sure. Another factor that effects the life of chrome plating is the hardness of the underlying steel.
Regards,
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |
May 20, 2011
Thanks for your reply, Ted. As I understand from your comment, due to higher thickness, a layer of hard chrome would be considered better. However, similar thickness layer would definitely make TDC a better option. As such we are considering the base metal of steels of EN series (EN8 and EN19, and P20 in certain cases ).
Jignesh Panchal- India
June 9, 2011
We currently spec our plating requirement for thin dense chromium plating to is AMS-QQ-C-320, however I believe that AMS 2460 supersedes this. However both specs are for general chromium plating. The relevant spec, I believe for thin dense chromium is AMS 2438 (thanks Dan Drummond). Now our plating supplier's standard conforms to AMS 2438A.
What is the difference between AMS 2438 and AMS 2438A?
Metallurgist - Plymouth, United Kingdom
December 7, 2011
Does AMS2460 specify raw material specification for chrome? Can these raw material specifications be related to ISO or ASTM standards ?
Thanks for your help
Franck
- Bordeaux, France
February 7, 2012
Hi Franck,
Unfortunately none of the AMS specs (2406, 2460, QQ-C-320) specify a raw material for the chrome.
Hope this helps.
- Metallurigst, Plymouth, UK