Powdery residue on Hard anodized 7075 parts 2

[elroy]

I recently had some large 7075 aluminum alloy parts hard anodized at a local Anodizer. The parts are covered with a powdery residue and look extremely dull in appearance. The anodizer has offered no explaination for the appearance of the parts. I quick google search suggests that the parts may have been processed "too hot" resulting in larger than normal pores in the anodize surface. Can anyone offer any addtional explaination for what may have happened? Can the anodized surface be repaired?

Thanks

 

[swall]

It may just be hard water deposits--what kind of water does the anodizer use for a rinse? It should be DI or RO, not just city water.Also, if the bath temperature was too high, you would have trouble obtaining max hardcoat thickness. What is your thickness requirement and where do these parts measure relative to your spec?

 

[TVP]

Do you require any post processing (sealing, PTFE impregnation, etc.)? I agree with swall that it may just be due to the final cold water rinse, but it may be possible that the parts were also immersed in another solution.

 

[elroy]

The anodize thickness is supposed to be .002" with water seal, no PTFE or nickel acetate sealant. The problem appears to be more than just a powdery residue. The residue is easily removed by wiping down the part with solvent. However, the anodize surface appears to be "unsealed" and very dull in appearance. I tried applying a thin coat of WD-40 to improve the appearance but the part soaks the oil up like a sponge. Within minutes, the surface is once again dull looking. It appears that my orginal suspision that the part is porous is likely true. I am thinking about having the part stripped an re-anodized but I am concerned about the loss of tight tolerance features on the part. Needless to say, this anodizer is no longer recieving my business