Posted by Scott Eastman (75.144.176.249) on December 02, 2008 at 17:41:39:
I am anodizing a highly machined block of aluminum. The parts come in generally very clean. The pretreatment is in-line with all other cleaning we do for similar materials of the 2000 series. After the black anodize process there are patterns in the material which have a poor adhesion of the anodize on the surface. There is noticeable spotting that occurs in these areas which bleeds out of the pores. The parts have been stripped in a caustic solution and desmutted in a nitric based solution then re-anodized and the same problem occurs. We do thousands of pieces similar to the ones in quetion with no problems. Any Ideas out there?