Metal finishing Q&As since 1989
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Hard Anodize - temperature - Pore density question
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Q. Can anyone give me an idea as to the different pore densities that would be produced by a hard anodize process - where the only difference was temperature? The bath concentration levels are the same for each of the three temperatures. the amps/ft2 are all run the same (say 35 amps/ft2). What would be the pore density difference between a bath that was 45 degrees, a bath that was 35 degrees and a bath that was 30 degrees? My understanding is that temperature obviously keeps the part cool from all the current running thru it - but does it not also have an influence on the shape and size of the pore?
Wedge McFrodyproduct designer / ex anodize job shopper - Houston, Texas, USA
May 21, 2010
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A. Quantitative data has not been published because the answer is in multiple variables. The general rules are: the warmer the solution then the larger the pores (less Taber Abrasion), the higher the free acid then the larger the pores, the LOWER the current density then the larger the pores. Glycolic/glycerin additives make the pore smaller.
Old fashioned oxalic acid makes the pore smaller. That is four dimensions right there and we have not added in dissolved aluminum, alloy, etc.so no hard numbers.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
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