The authoritative public forum
  for Metal Finishing since 1989
-----

Blisters in the hardcoating process

I am a quality manager at an finishing shop. I am looking for information on what causes blistering in the hardcoat process. The problem does not seem to be alloy specific. 2011 alloy and M1 alloy have both shown this appearance recently. I have also seen blistering on 7075 not within the last 4 years. Any guidance would be appreciated.

Thanks,

Timothy Berry
Anodizing Shop. - Detroit, Michigan, USA
2004

---

2004

Too thick hard coat on inside curves will crash the growth and fracture. Anodizing over work hardened surfaces will exfoliate if too heavy thickness Anodizing over embedded trash from steel shot peening, time savings, tumbling, etc will exfoliate.

Anodizing over partially intermittent old aluminum oxide left behind by inadequate deoxidation and usually following heat treatment, that too, will exfoliate.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina