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topic 60510

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


A discussion started in 2017 but continuing through 2019

September 15, 2017

Q. I am looking into coating a washing machine part called a spider arm. AFAIK, it's made of die cast aluminum.
The part bolts to a stainless steel drum, which it spins. 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.

60510-1a 60510-1b

I am getting ready to put in a new spider-arm and i would like to treat/coat it so that i could get at least 10 years out of it. The coat of course has to be durable, adheres well to die cast aluminum (with the right prep work), resistant to alkaline water, soap, heat (100 °C/212 °F), bleach and bio-films.

What do you guys suggest?

More pics from google: https://www.google.com/search?q=spider+arm+corrosion&safe=strict&client=opera&hs=ocg&source=lnms&tbm=isch&sa=X&ved=0ahUKEwif2dmc8KXWAhXBcRQKHanTDLMQ_AUICigB&biw=1517&bih=745

Elliott Wright
- Thuwal, Jeddah, Saudi Arabia


September 2017

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,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


September 17, 2017

Q. Thanks for your input Ted!

Since I've posted this question a few days ago, I've been looking into powder coating. I hear it's superior to 2k epoxy paint. I'm open to suggestions.

I am not sure though what kind of powder coating to go with - if powder coating would indeed be a better option.
Thermoset or thermoplastic? Fluidized bed method by heating the part, or electrostatic fluidized bed method? And if fluidized bed method instead of spraying, then what kind of powder...nylon? PCV? If using a gun, then again...what kind of powder?... Epoxy? polyester etc.?

What about pre-treatment? I hear conversion coating is best...but what kind?... Phosphate? Chromate? Oxide?

The conditions the spider will be in is basically aquatic - lots of soap and water, occasional bleach, and heat (100 °C/212°F).

Elliott Wright [returning]
- Thuwal, Jeddah, Saudi Arabia


September 2017

Alodine 1201

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,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


September 18, 2017

Q. When it comes to die cast aluminum, what is the best way to clean the surface before chromate conversion? What kind of a deoxidizer will do the job, so there would not be any traces of silicon, copper, etc. to ruin the end result, which is powder coating?

A step-by-step instruction would be so greatly appreciated!

Elliott Wright [returning]
- Thuwal, Jeddah, Saudi Arabia


September 2017

A. Hi again Elliott. "The Surface Finishing and Treatment of Aluminum and its Alloys" [link is to info about book at Amazon] 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,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


September 19, 2017

Q. Thanks Ted!

If i were to go with what you suggested at the end, wouldn't NOT properly cleaning it (desmutting etc.) before Alodining cause problems with the paint (epoxy) later?

Elliott Wright [returning]
- Thuwal, Jeddah, Saudi Arabia


November 2017

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,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



November 28, 2017

Q. I am in exactly the same boat. I have a new spider arm that I would like to do something to before putting this all together again. My machine lasted only 2.5 years!

Is there a simple process I can easily do from home?

What did you end up doing?

Michael Hornick
- Mississauga, Canada


November 2017

A. Hi Michael. What I would personally do is scrub with a solution of pumice and detergent, rinse and dry it. Then apply self-etching primer designed for aluminum, then epoxy coat it. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



December 30, 2018

! I went to do a washing load and I heard a terrible noise from my washing machine ... I knew it was the shaft that was broken.

60510-2broken

It could spin by itself but without any force; so today I fixed my Spider Arm/Shaft on my Samsung machine. Using the video below it's not that difficult at all -- it just takes time.

Purchased the part (DC97-12528A) at https://electropiecescowansville.com
Helpful Video to disassemble the part: https://youtu.be/gTXoKMHHpLs

I gave 2 coats of Rust-Oleum Specialty Appliance Epoxy Paint on the shaft.

Here are the results:
Before & After --

60510-2b4andafter

New part painted and reassembled --
60510-2reassembled

Let's see how this stands up.

Anthony fix
- Canada quebec


December 2018

thumbs up sign  Thanks Anthony. Great job, and nice graphics. By the way, anyone anywhere wanting to make an instructional video should watch that video from AppliancePros first ... What an incredibly clear and perfect illustration and explanation video!

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


May 7, 2019

3M Marine Sealant

A. These spider arms corrode where water sits on them after washing. That's in the rings near center. the sitting water might eventually soak through the paint. I would fill all the crevices with body filler to make it all smooth so there is nowhere for water to stand, then primer & paint it. You could also coat & fill it with 3M 5200 high strength marine adhesive. It is made for boat hull transoms. Manufacturers use it to stick the keel on the underside of boats. It can stay wet forever & the boat will break before the 3M 5200 ever does.

The spider pot-metal looks similar to that of outboard boat motors. I might try some outboard-motor paint over a zinc-chromate primer.

Michael Haiducek
- St. Louis, Missouri



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