90% of the work i do is 7075 aluminum, and it usually comes out great. However, i am having an issue with one particular part. It has a greyish color to it and it seems to be overly pourous after anodizing. When i dye it and seal it, it tends to have a blotchy blackish tint and will dye REALLY dark if i leave it too long in the dye. This is only with these particular parts, which are made out of 4" diameter bar stock. The other parts are made out of .125" thick sheet, both 7075. I generally run both types of parts at the same time if they are the same color, and the parts made out of the .125" thick sheet come out perfect so this makes me think my setup must be ok. Agetation and temp are decent (about 70 degrees), and i run 6asf. I generally keep it at about .8-.9mil, and i reduce the time by 25% due to the alloy being 7075. I etch and desmut/deox. The parts that come out poorly are approximately 12sq inches. The parts that come out great are approximately 21-46sq inches. Again, i run both of these parts together in the same run, so i just find it weird that one part consistently comes out poorly and one always comes out great, and they’re both the same alloy.
If i was miscalculating my ASF or my setup was wrong, wouldnt everything have dissolution? My guess is the aluminum is the aluminum might be the variable that is giving me issues, but i cant figure out why.