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View Full Version : Cheap Small Quantity Chemical Resistant Coating



scott123
01-09-2017, 05:55 PM
The shaft on my dishwasher pump motor is already pretty rusted, and I'd like it find a way to keep it from rusting further- at least until I replace my washer in a few months. Based on the way the seal works, the shaft sees a few drops of drain water during use, and is most likely damp the rest of the time. According to my calculations, my normal cycle (cascade) produces drain water in the 10 pH realm and, after that, I'll typically do a citric acid rinse that's about 3 pH. I also occasionally do citric acid rinses on their own, but a rinse involves two 7 minute cycles, so, hopefully, the second, water only cycle, should bring the pH up a bit.

Basically I'm looking for a coating that will offer good resistance to intermittent exposure between 3 pH and 10. And I'm looking for the cheapest option possible. 2 part epoxy paint would certainly give me the chemical resistance I'm looking for, but it's way more than I'm willing to spend on this washer- and it typically comes in quantities of far more paint than I need.

For reference, this is the type of motor I have. The only difference is that the corrosion on my shaft is at the bottom/next to the slinger, rather than the rust at the top you see here.

http://i.ebayimg.com/images/g/4lwAAOSwpRRWnN5m/s-l1600.jpg

ed_h
01-09-2017, 06:08 PM
Something like POR15 would hold it for a while, but even the little pint cans are not cheap.

How about coating it with JB Weld?

Ed

scott123
01-09-2017, 09:31 PM
How about coating it with JB Weld?

I've thought about JB Weld. I'm reasonably certain that JB Weld gives me the chemical resistance I'm looking for, but... there's not much clearance between the shaft and the plastic impeller that sits on top of it, so I need something that's thin enough that it will paint on in a fairly thin layer. From what I can tell, thinning epoxy is a sketchy endeavor. I can find research on the loss of compressive strength via dilution, but that means a lot less to me than potential shrinking (cracking) and porosity, and I've found nothing on that.

This epoxy paint here (http://www.epoxy-coat.com/index.php/msds), at first glance, seems to use benzyl alcohol as a thinner, and I'm tempted to combine JB Weld with benzyl alcohol, but, much like epoxy + other thinners, the track record for my application is non existent.

J Tiers
01-09-2017, 10:57 PM
Or just plain 5 minute epoxy? Should paint on and stay decently, cheap, you may already have it, and if you do not, it is multi-purpose, it will likely get used.

LibbyHillBrewer
01-10-2017, 12:08 AM
Just give it a good coating of clear polyurethane. It's only going to be a temporary fix anyway so there's no use going overboard on industrial coatings.

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6PTsocket
01-10-2017, 03:35 AM
Moisture curing poly or 2 part poly might work but isn't stuff like Minwax poly and other 1 part poly indoor stuff? The first two are industrial and expensive. Some of the outdoor and auto paints are water proof but are not food approved and even if it is the dish washer that is too close for me. There must be a real iron problem to require all that citric acid. Is it rusting parts or just rust stained parts? Is it just metal parts or on everything?

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dian
01-10-2017, 03:46 AM
i always thought a zink coating was the cure.

Fasttrack
01-10-2017, 08:53 AM
Why? If you are replacing it in a few months anyway, why not just keep using it? It's not going to rust through in that time...

If you've got room, you could put a sleeve of waterproof heat shrink tubing over it. It has a hot-melt adhesive inside and is used for making splices in buried cables, among other things. For example: https://www.mcmaster.com/#heat-shrink-tubing/=15umrw9

Ed ke6bnl
01-10-2017, 09:48 AM
we use to coat the out door AC fan motor shafts with thread eze and years later we could remove the 2 in shaft running through 4 fan assemblies with ease, planned a whole day for the job that took a few hours.

scott123
02-21-2017, 03:12 PM
UPDATE: I had to put this project on the back burner for a bit, but I have a little time now. At the moment, I'm teetering between jb weld diluted with acetone (both of which I have on hand), vs. jb weld diluted w/ a $5 bottle of benzel alcohol from etsy. I spent some time researching a new dishwasher, and, based upon the number of models with seal issues, I'm leaning towards nursing my old machine along for a while- maybe a year or two. Devil I know vs. the devil I don't. I may replace my motor for about $30 (used), but I'd still like to zero in on a means of preventing the shaft from rusting, so I continue to be open for suggestions.


There must be a real iron problem to require all that citric acid. Is it rusting parts or just rust stained parts? Is it just metal parts or on everything?

Citric Acid does two things for me.

1. I have very hard water, so it keeps deposits off.

2. I'm sure someone here knows the chemistry better than I do, but, during a pre-soak, citric acid seems to be a bit more effective with dairy based residue than water alone. Dairy residue is typically not a huge issue (eggs are my mortal enemy ;) ), but every little bit helps when it comes to making sure the dishes end up clean.

There's probably a quantity of acid that I could use that would lower the pH just enough to prevent deposits while not attacking my shaft coating, seals, etc. The real issue, though, is that I have a family member who is extremely allergic to industrial perfumes, so even though the Cascade I'm using does an excellent job of getting the dishes clean without an acid pre-soak, I'm playing with fire by using it, so, ultimately, I'm going to have to work out a phthalate free solution. Based on the abysmal results I've gotten from commercial natural dishwashing products, my phthalate free solution will most likely be my own- and, will most likely have an acidic component.

In other words, even though, technically, I could get away without using acid, I need to have that option open in the future.


i always thought a zink coating was the cure.

I briefly thought the same, but zinc with acid- no good.


we use to coat the out door AC fan motor shafts with thread eze and years later we could remove the 2 in shaft running through 4 fan assemblies with ease, planned a whole day for the job that took a few hours.

Thread eze is typically zinc based. See above.

darryl
02-21-2017, 08:51 PM
Floor wax.