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topic 7899

Dimension Change After Hard Coat


What is the dimension change that should be expected after hard anodizing? I thought that this would be easy to find, but have not been successful. The material in question is 6061-T6, hardcoat per Mil-A-8625 [link is to free spec at Defense Logistics Agency,], Type 3, Cl 1. Thanks for the help.

larry hanke
Larry Hanke
materials testing laboratory
Minneapolis, Minnesota


"Hard coat"of itself does not call out a thickness. The mil spec does, but allows a + - 20% variance in thickness. Therefore calling out a total dimension will help. Bare in mind that 1 mil thickness of hard coat will give you approximately 1/2 mil buildup since part of the coating is created from the base metal.

I hope this answers your question. I also hope that if I am incorrect some one will let me know.

drew nosti
Drew Nosti, CEF
Anodize USA - Ladson, South Carolina



Typically the build up for hardcoat is 50% of the total coating thickness. Therefore, on a typical 2 mil hardcoat, one would expect to see a buildup of 1 mil per side.

Marc Green
Marc Green
anodizer - Boise, Idaho


Generally speaking Type III coatings build-up 50% of the total thickness. The default for the milspec is .002"(+/- 20%) which would be equal to .0008"-.0012" build-up per surface. Keep in mind threads build up 4x as much so it may be a good idea to mask threads.

Hope that helps!.

Bill Grayson
- Santa Cruz, California, USA


I have always found when working with hardcoat that it is safe to assume .001 penetration and .001 buildup.

J. Scott Clinton
- Philadelphia, Pennsylvania, USA

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