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What is the best way to treat/coat (die) cast aluminum to prevent corrosion?

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  • What is the best way to treat/coat (die) cast aluminum to prevent corrosion?

    The aluminum part i want to protect is part of a washing machine. It's called a spider-arm, and it's attached to a stainless steel drum. The drum is of course where you put your clothes. It spins at speeds of 1200rpm. The load (clothes) can be unevenly distributed in the drum during a spin, therefore it probably goes through high stress. This setup is (afaik) only on front load washers.
    Click image for larger version

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    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, not using bleach...and so on.

    Those who say it's NOT 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 up 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. What would be the best method?

    Greatly appreciate any help i can get!

    Click here for more pics (Google image)
    Last edited by yman; 08-13-2017, 05:30 PM.

  • #2
    If I understand you correctly, its the aluminum thats the problem.Why not take the new aluminum spider to a plasma shop and have then cut a new on from stainless steel? We often do this in our shop for the local farmers and ranchers. Even a few dairy's. Some of the ranchers and farmers just abuse the ****ens out of their equipment and when they find out what a new factory replacement costs, they look for other alternatives. We have made some replacement parts that looked futuristic. Just a thought.

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    • #3
      Wow, bad stuff. Alkaline detergents are bad news for aluminum. Some may contain washing soda (sodium carbonate) which is what is used in an electrolytic derusting tank. Low pH.

      I think Kitchen Aid says not to wash some of their aluminum mixer attachments in the dishwasher for this reason.

      Here's the fix: homebrew stainless steel spider: https://www.youtube.com/watch?v=XCytwzIbzO8

      Or use Deft aircraft epoxy paint like this guy: https://youtu.be/4Pig2UQk18c?t=4m48s

      Alternative paints might by Glyptal enamel or epoxy propeller paint:

      http://www.skygeek.com/tempo-a152-wh...r-coating.html
      Last edited by usmcpop; 08-14-2017, 10:50 AM.
      --- RJL ----------------------------------------------

      Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
      -------------------------
      DialArc 250 (1974), Idealarc 250 (1971), SyncroWave 250 w/Coolmate 3, SP-175+, TA 161STL,
      Lincwelder AC180C (circa 1952), Victor & Smith's O/A, Dayton (Miller) spot welder, 1200 sq.ft. of garage filled with crap and a kid that can actually run the stuff +++

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      • #4
        Originally posted by Hunter55 View Post
        If I understand you correctly, its the aluminum thats the problem.Why not take the new aluminum spider to a plasma shop and have then cut a new on from stainless steel? We often do this in our shop for the local farmers and ranchers. Even a few dairy's. Some of the ranchers and farmers just abuse the ****ens out of their equipment and when they find out what a new factory replacement costs, they look for other alternatives. We have made some replacement parts that looked futuristic. Just a thought.
        I agree with the solution above, since this seems to be a clear case of the wrong base material for the function.

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