How to protect cast aluminum from corrosion?
How to protect cast aluminum from corrosion?
(OP)
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, therefore it could be put through high stress. This setup is (afaik) only on front load washers.

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)

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)





RE: How to protect cast aluminum from corrosion?
RE: How to protect cast aluminum from corrosion?
RE: How to protect cast aluminum from corrosion?
RE: How to protect cast aluminum from corrosion?
RE: How to protect cast aluminum from corrosion?
so far the industry has not come up with a suitable solution, a water soluble bactericide that is effective in killing the bacteria in the environment of a washing machine while being ecologically acceptable has not yet been found.
you could call the use of aluminium a design flaw. however, you need a material that is both relatively light and strong - modern plastics so far seem to be unable to fulfil those requirements.
coating the spider with a coating that makes the aluminium out of reach for the bacteria might be a solution. apart from paints etc as suggested i think powder coating the specific part might be a solution. with that you probably can get a denser coating then when applying it with a brush.
the speed at which the spider rots away is highly dependent on local water quality - and water quality may vary quite a bit, even in the same city.
RE: How to protect cast aluminum from corrosion?
RE: How to protect cast aluminum from corrosion?
RE: How to protect cast aluminum from corrosion?
RE: How to protect cast aluminum from corrosion?
The AI arm bolts to the stainless steel. Would tightening down the bolts break the powder coating?
RE: How to protect cast aluminum from corrosion?
Your problem would come in when the modestly thick powder coating plastic layer (applied as a sprayed-on powder then melted in a furnace) would fill-in drilled bolt holes, or cover a surface where the arms attach so the stack height of the assembly is too big.
RE: How to protect cast aluminum from corrosion?
Your problem would come in when the modestly thick powder coating plastic layer (applied as a sprayed-on powder then melted in a furnace) would fill-in drilled bolt holes, or cover a surface where the arms attach so the stack height of the assembly is too big.
You mean clearance might be an issue?
RE: How to protect cast aluminum from corrosion?
RE: How to protect cast aluminum from corrosion?
Second, there is no such thing as aluminum eating bacteria! That set my BS meter off immediately. There are bacteria that excrete acids that will corrode aluminum.
Third, this part looks like it could easily be replaced with a stainless steel stamping. With a little development it probably could match the weight, strength and cost of the aluminum part.
If there is really much of a market for such a thing, the OP should take the entrepreneurial initiative and start the ball rolling. I expect the market is actually very small, only places with the wrong water conditions.
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