Blistering in hard anodize on 7075 aluminum

[BlaineW]

Has anyone seen small bubbling/blistering on a hard black anodize when doing 7000 series aluminum. I've looked around on the net and found many instances of it, but none of the answers or reasons for why it happens or how to fix it agree with one another.

Thank you for your help

 

[mcgyvr]

What is the temperature you are anodizing at? A higher temp might help.
(should be like 50 deg F at 36 asf)

Bath contamination?
electrolysis or electrolytic corrosion in the dye tank?

 

[coatingengineer]

Hi.

Most dyes are pH-sensitive. And, in hard anodize heterogeneous alloys of aluminum like Series 7000, localized 'spikes' in pH are not uncommon.

So, how is it occurring?

Take a look at your part geometry. Is the phenomenon localized? Is it near your points of contact?

How's the quality of machining? Has the grain structure been measurably altered in finishing?

For more information, see:
<a href="http:

http://www.industrialcoatingsworld.com/Wear-Resistant-Coatings/Anodizing-.html">Anodizing</a>

Good luck!


William Gunnar

http://www.IndustrialCoatingsWorld.com