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Is it OK to spray epoxy primer over anodized cast aluminum?

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  • Is it OK to spray epoxy primer over anodized cast aluminum?

    What is the best method of protecting cast aluminum from corrosion when it will be attached to stainless steel and dumped into sea water where it would reside for 10 years without any access to it?

    The aluminum part i'm talking about is called a spider-arm...found inside a washer It's attached to a stainless steel drum. The drum is of course where you put your clothes. This setup is (afaik) always on a front load washer. The thing is, the spider always corrodes and breaks - mine did in just 3 years. It's inevitable. Lots of theories as to why that happens...galvanic corrosion, water PH levels, too little detergent, too much detergent, using cold water, keeping the washer door closed...and so on.

    Those who say galvanic corrosion argue that if it was, the spider would have corroded at the points where it meets the stainless steel drum (the 3 ends), and at the shaft. Although most of the corroded spiders i've seen corrode a few inches from the shaft, i'm yet to see most of the corrosion happening at the spider-arm end joints...or immediately at the shaft. So they are of the opinion that the reason it is corroding is because of soap and high PH water.

    In any case, i am getting ready to put in a new spider-arm and i would like to treat/coat it (and/or the stainless steel directly under it) so that i could get at least 10 years out of it.

    I am thinking of first etching it with phosphoric acid, then anodizing it, and finally spraying it with a 2 part epoxy primer. What do you guys think?
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  • #2
    I'm not sure about anyone else but I do have a few thoughts. You'd be better off scratching the surface with a medium grit sand paper. Don't waste money on anodizing. All your doing is increasing the oxide layer ever so slightly, it won't have much effect in my opinion.
    As for the 2 part epoxy coating, find the stuff used in off shore paint applications. It goes on as a heavier coating, as well comes with corrosion inhibitors.

    Another thought might be build it better. Just because they built it out of aluminum doesn't mean you couldn't have one fabricated out of stainless? With the cost of a replacement and the extra work you have planned to increase it's life expectancy, could be worth your while to salvage the center and adapt it into something you make?

    My other thought would be reinforce what's existing. Again just a thought?

    As to what's causing it why and where, above my pay grid.

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