What kind of coating for washing machine's aluminum spider arm?

A. Hi Elliott. As you say, this is a perennial problem for buyers of front-loading washing machines.

opinion! A similar question was asked in the early days of finishing.com 20 years ago, and it seems that no washing machine manufacturer has much interest in fixing the problem as long as it squeaks through the warranty period so the repair cost is shifted to the consumer. If there are class action suits, I think the manufacturers would be forced to admit that using an aluminum diecasting for hot, alkaline, immersion like this is a well-known design defect. Bleach is extremely alkaline and dissolves aluminum; minimize its use if you can :-(

The right answer of course is to make the spider arm from a stainless steel stamping. That isn't practical for home repair, but some home craftsmen have done second best and made them from stainless steel weldments. Short of that, the aluminum can be epoxy coated, preferably after thorough cleaning and Alodining, which ought to somewhat extend its life, although I don't think "at least 10 years" is likely no matter how you paint aluminum. It would be theoretically possible to electroless nickel plate it, but you would find the cost prohibitive. Good luck.

Regards,

Alodine 1201

on eBay or

Amazon

(affil links)

A. Hi. Alodine is chromate conversion coating, and the best pretreatment for aluminum. I don't think powder coating is better or worse than epoxy paint -- proper pretreatment plus full coverage matters more.

Regards,

A. Hi again Elliott. The Surface Finishing and Treatment of Aluminum and its Alloys [adv: suggestions on AbeBooks, Amazon & eBay affil links] is over 1300 pages, so it's tough to start from scratch and condense the subject down to "step-by-step" and of appropriate length for a public forum response :-)

But in a production situation the component would be vibratory finished, then immersed in a mild alkaline cleaner, then immersed for light etching in strong sodium hydroxide, then de-smutted before the chromate conversion. But the best de-smutter will depend on the exact alloy: for example, nitric acid to deal with copper, fluoride to deal with the silicon, or most often a tri-acid desmutter.

Topic 45313 offers many perspectives on the subject of pretreatment for chromate conversion coating, but people do not use these techniques and extremely aggressive chemicals for one-off treatments in a home environment, but only in an industrial factory after they have received hands-on haz-mat training and have been supplied with appropriate personal protection equipment, and also have appropriate disposal facilities for the chemicals.

If I were you, I would scrub it with pumice powder and detergent, rinse it, dry it, Alodine it, rinse it, and paint it with 2K epoxy.

Regards,

A. Hi again Elliott. Certainly it's not "ideal" to skip desmutting, but compromise is part of life. For us to suggest that a consumer, in presumably a residential situation, working on a single spider arm, de-smut the aluminum alloy with nitric & hydrofluoric acid would be an abominable idea :-)

Regards,

A. The spider is not made from aluminum it is made from zinc. The manufacturers have no intention of fixing it because they have done it intentionally. Zinc corrodes and eventually disintegrates, that is the whole idea: sell more washers.

Here is what I did, washed it with a degreaser used a wire brush on a drill to rough it up, then a phosphoric acid etching. Followed by a zinc dust ⇦this on eBay or Amazon [affil links] and a couple of coats of Rust-Oleum camouflage paint. It is tricky to get the paint in all the little crevices but if you hold it in your hand and rotate it as you touch up the paint you can do it. Baked it in the oven for 3 hours at 200 °F. Removed the little o-ring from the shaft prior to baking. It looks really good, only time will tell if it will last. Regarding the Rust-Oleum camouflage paint, I know it must sound like a strange choice but it is very tough, very fast drying and gives off little odor.