on a combination washer/dryer, there's one metal part called the dryer duct, where water vapor right out of the drum is heated some more before going to cold water bath to condensate.
That vapor apparently carried a lot of soap with it, and after a few years there's almost 0.5Kg of soap there. I took it all apart for cleaning and there's soap under the paint, which is just flaking out.
I'm now removing all the paint and soap. The part is still pretty good. appears to be aluminium. and there's a heater element that goes right in it, so there's no rust showing anywhere.
Should I try to paint it again? with what kind of paint?
I'm guessing that if it didn't rust with all that humid soap under the paint for all those years, that it's mostly cosmetic.
I tried to buy a new one, but it's not made any more.
it was not dry soap after all. it was Al oxide dusty, i think. anyway, it was definitely not dried soap.
i ended up using a drill with a steel wool bit to make the entire part shinny.. removing the dust thing and the old paint. then painted it with a bbq grill enamel spray paint.
I would love to be able to inspect it regularly, but it is a major pain. I sealed the part with high temp silicon glue. also, disassembling the appliance enough to remove/open the part is a 4h job...
I did all that a few days after i posted this question. So it's been working perfectly for 9mo... i guess it worked out fine. I will try to inspect the leaving water for Al oxide dust tho. but not sure how i will do that...
The heating element, which appears to be a sort of steel aloy has no rust signs. The two screws hold it inside appear to be another Al alloy from the color (i'm no expert on metals) and are fine. I'm guessing the Al alloy used for the part was not up to spec for the temp changes and chemicals involved in the washer/dryer combination expected use. Typical LG cost cutting :(