Paint adhesion 6061 vs 7075

[MMike1]

Would anyone know if paint just inherently adheres better to 7075 than 6061?

We've been doing some in-house comparisons. We use 6061, and our competitor uses 7075. And their primer seems to stick better. We are alodining the parts.

But before I dig too deeply, I'm just wondering if it's due to the base material itself, or if it's the paint/prep.

 

[coatingengineer]

Hi. Paint adherence will be affected by surface preparation, you know. Are surfaces touched after Alodine but prior to painting? Bonds between your paint and substrate are mechanical. That said, is your competitor adding grit blast or anchor pattern by phosphate conversion ground coat? Chemical differences between 7075 and 6061 should not matter for you.

William Gunnar

http://www.IndustrialCoatingsWorld.com

 

[TVP]

Agreed, there should be no substantial difference between the two alloys in terms of paint adherence.

 

[KENAT]

Have you compared the Alodine coatings between yours and vendors parts?

There are different grades of chem film. There is a grade that maximizes corrosion prevention at the expense of electrical impedance. Then there's a grade the minimizes impedance at the expense of poorer corrosion prevention. Then there's the ROHS versions.

I'm not sure if or how this affects performance as a substrate to paint though.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[MMike1]

Well upon closer inspection yesterday, it would appear that the competitor actually anodizes, rather than just alodines.

Soooooo.....I think that might have a little something to do with it. (gee, ya think?)

Thanks all......

 

[boothuk]

Wettability of the surface will generally increase with surface pre-treatment. (Acid / Alkaline etch, etc.) The alloys won't possess significant differences in adhesion as an untreated surface.

 

[drawoh]

MMike1,

The chemical films are used extensively as paint substrates. If the paint finish really mattered to me, I would avoid anodizing.

JHG

 

[swall]

drawoh--anodic coatings on aluminum have an extensive history of useage as paint bases in the aerospace industry.