Metal finishing Q&As since 1989

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Type ll anodizing buildup VS. coating thickness

I been in the metal finishing business for a while, but I have a dilemma, The person who was teaching me anodizing on aluminum told me that the type ll anodize have minimum buildup, but we use an isoscope to measure the coating thickness on the parts and regularly we get about .0006"-.0009" but a customer told me that he measured an ID on one of his parts he told me he got .0002" buildup per surface.

My question is... Is the coating thickness equal to the buildup? and like hard anodize; is 50% buildup 50% penetration, what is the ratio on type ll ?

Sergio G.
- Oxnard, California
2002

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2002

While people note that the anodize buildup is not exactly 50-50 depending on the alloy, the thickness, and other conditions, I am very comfortable with the way the AESF RTC phrases it, i.e., "approximately half"; whereas if someone says it is 55.413-44.587, we need to be wary of the old engineering bugaboo of precision without accuracy.

If your customer measured a decrease of .0002" on each side of a hole, the thickness of the anodizing in that area is approximately .0004"; I wouldn't attempt to put a finer point on it.

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

Actually, the measured "build-up" for type II is about 33% of the anodic coating per side. The warmer tank temperature allows for a faster dissolution rate than type III coatings. -Bill.

Bill Grayson
- Santa Cruz, California, USA
2002