Blueish discoloration on hard anodized parts

A. Apparently the oil mist is getting into the pores, worse in the lower current density area where then pores are slightly larger.

A. Hi Afiq. I think Robert's reply implied that a blue discoloration like this is not a known defect in hard anodizing. Therefore the chance that the alloy or something out of spec in the anodizing process, is the cause of the problem sounds extremely unlikely. On top of that, you didn't have the problem until recently and it's occurring on two distinct anodizing lines :-)

Please tell us the alloy and we can research whether there is anything special about it. But if you don't accept that the problem is in the operating environment rather than the alloy or the anodizing process, the only way forward would be to get some material from a different supplier and see if the problem persists, and for the supplier to ship his material to a different shop and see if the problem persists there. The environment in your shop or that the parts are exposed to before they get to you is causing the problem, and my bet is your shop rather than before you receive the material. Best of luck!

Regards,