7075 HARD COAT BLISTERS

[LONDONDERRY]

We received a loy of parts back from a vendor. The material is 7075-t6 aluminum thta ts hard coat anodized. The first batch originally done looks and feels like hard coat. The second batch done 4-5 months later, the parts look blemished and not as smooth as the original batch. I sent the parts back to the vendor and they in return visted the finishing shop, which told the machine shop that its a metallurgy issue with the material. I've done some research into this issues and I've come to the same conclusion. However, from what I've read here and there it may all so be a finishing as well. Has anyone elese experienced this and give some insight on if its a finishing or mill house issue, and any ways to correct this for future parts being made?

Regards
Frank

 

[Ron]

It could be either. Have a metallurgical evaluation done on a good piece and a bad piece to see if there's an appreciable difference in the metallurgy. Also, have an SEM/EDS scan done on the failure face to see if there was a surface prep or chemical problem as well.