View original topic: Rustoleum metal primer UNDER epoxy primer?
epowell Sat Sep 19, 2020 1:40 pm

Hi Folks...
I'm back in BC and ready to start some major underbody rust removal on my van here.
I'm in quarantine now so might go and pickup my 1 litre of epoxy primer 12 days from now...

....what I am thinking to do now is get my mom to go to the local store and buy some ordinary metal primer paint. Then day by day as i grind off more rust, I can just quickly slap on some of this cheap metal primer as a way to immediately seal the bare metal. Then later I can apply top quality epoxy primer to the entire affected areas.
--- does anyone see any problems with this plan? For example could there be an adhesion problem for the epoxy primer since the initial layer over bare metal would be the generic 1 part metal primer?

BCgee Sat Sep 19, 2020 1:58 pm

Not sure why you would apply a metal primer under an epoxy primer: seems what you want is a rust negator. I suggest you deal with the rust by either cutting it out and welding in fresh panels or grinding down to good metal, then treat any remaining dubious areas liberally with Ospho. Ospho neutralizes rust by chemically changing it. Then, after doing Ospho, dry time, and neutralizing the Ospho, apply epoxy primer. Last, paint. This strategy has worked well for my topical and mellow seam rust; learned from Jeep 4x4 friends. Good luck.

dobryan Sat Sep 19, 2020 1:59 pm

You'll need to remove the spray can primer before you put on the epoxy primer. Otherwise the epoxy primer is only bonding to the layer of primer you previously sprayed on.

Can anyone else pick up the epoxy primer for you?

epowell Sat Sep 19, 2020 5:51 pm

OK, so best not to mess with the initial layer of cheap metal primer... part of the reason I wanted to do it that way is also quicker and easier than everytime with 2 part epoxy paint... rather just do that once.

I'll find out exactly where the store is and ask my mom to go there - she's pretty cool :)

nemobuscaptain Sun Jan 10, 2021 10:15 am

I've dealt with this Rustoleum metal primer and the "metal convertor". It is obviously total crap. I would never buy another bottle. It became immediately black, which made me suspicious because I've seen real metal convertors take a day or two to turn. I sprayed it on some white wood and it immediately turned black. It's just some shtttty rustoleum black paint.

I would use Ospho. It works great but takes a few coats and a day of curing in between. Going to also try Klean Strip Concrete and Metal prep because it is available locally (Home Depot) instead of mail order and appears to be the same stuff. All the products appear to be phosphoric acid of various concentrations. You need wire brush it first to take off the flake. Mine formed some white looking substance the first two coats. Just wash it off.

I agree, treat it with some phosphoric acid treatment and cover with epoxy primer. We have 2k epoxy primer at our local auto paint store in cans. It isn't cheap like Rustoleum but the cans do go a LONG way. This can solve your need to get some cover on bare metal as you are doing work bit by bit.

Even clean metal, ospho says to dilute 1:3 with water and can be used as a prep.

BCgee Sun Jan 10, 2021 10:33 am

Another vote for manual rust R&R, then Ospho, epoxy primer, lastly paint.

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