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Powder coat or paint a rear subframe. Which is best? (3 replies)

Steve Hills
4 months ago
Steve Hills 4 months ago

I've got to the stage of blasting and painting my rear subframe. I'm planning to use the one that came with the car, a MOWOG wet subframe that I believe was fitted in about 1980, replacing the original. It's in remarkably good condition but with some surface rust and a lot of old smoothright patches. It's never been undersealed.

Given the choice between painting and powder coating. I've heard some people say how fantastic powder coating is and others say it will crack off and water and so rust gets behind the coating.

Anyone have any thoughts?

https://www.minicooper.org/wp-content/uploads/2019/04/Mini-rear-subframe-as-out-of-car.jpg

Steve

mgb
4 months ago
mgb 4 months ago

I would not go down the powdercoat route. Powdercoat is not flexible and if there is any flexing of the subframe, and I'm sure it will be, tiny cracks develop which will allow moisture to enter and creep along under the coating, it will not be obvious until the coating starts to bubble by which time there may well be a hole through the metal.

I have used Rustbuster's EM121 Epoxy for a number of years, being an epoxy, the molecular structure allows it to fill the tiny pits in the surface of the metal meaning that no air is trapped, unlike a polymer based paint that flows over the peaks. If you want the original painted look, you can spay the epoxy and then spray over that with black paint.

Steve Hills
4 months ago
Steve Hills 4 months ago

Thanks for your advice.

Steve

Steve Hills
3 months ago
Steve Hills 3 months ago

I'm getting on well with Rustbuster Epoxy EM121. Thanks for the pointer to that.

I tried a test. I had some thick aluminium foil, a food container that had been used to cook some in. I ensured it was very clean and de-greased, a cycle through the dish washer in fact.

I hand painted the bottom of the container with black EM121 then left it for a few days. Now you can bend the foil 90 degrees backwards and forwards lots of times and there's no sign of the EM121 cracking, flacking or peeling. Attack it with my finger nails and I can't mark it or peel it off. And that's bonded to aluminium, not steel, so pretty impressive.

The only thing is that you can't brush paint it without it looking brush painted. I may get a compressor and spray gun and give that a go.

Steve

 

Steve

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