plating, anodizing, & finishing Q&As since 1989
Anodize Buildup Question [Massachusetts]
July 23, 2010
Hello, I have a part (6061 Al.) with (18) .35 mm holes going through 9 mm thick piece. My question is how much will these Holes close up after Anodize. After finish inserted into these Holes are "Pogo Pins" that are .30 mm diameter. My dilemma is these Pogo's have to Slip Fit without wearing any of the Anodize off because Electric conductivity issue. The Part will also be under Vacuum.
Thank You for your advice.
Designer - Malden, Massachusetts, U.S.A.
July 27, 2010
Hi, James. Anodize buildup is approximately 50 percent of the anodizing thickness, with the other 50 percent going into the substrate (i.e., about .02 mm of aluminum substrate is consumed to make .04 mm of anodized coating). So the hole diameter will decrease by about the thickness of the coating. A .04 mm coating on a .35 mm dia. hole would leave you with a hole of about .31 mm dia.
The "numbers" should work, but that doesn't necessarily mean it will be easy and practical :-)
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 30, 2010
Exactly what Ted Mooney said PLUS the 50/50 can vary 60/40 up to 40/60 as a function of the alloy, free acid, solution circulation through the hole, temperature and current density - so budget for 50/50, then measure and adjust for your particular conditions. Regarding all of the above, the thickness will "dog-bone", closing more of the top of the hole and less of the middle of the hole, again a function of solution circulation through the hole.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina