The Stovebolt Site Forums The Shop Area Paint and Body Shop Using Ospho

First things first.....I am NOT a paint and boy man and never will be.....I'd read and remember very little so here goes.

Simply question.....if you wire brush, lets say a floor pan, and have it fairly decent and want to stop any future rust, I understand it needs to be, or can be treated with ospho before doing anything else.
So, If I spray the "floor pans" with ospho do I have to wash it off with water???....or can I let it dry, then put POR-15 straight on top of it.....OR...even just spray paint over it without doing anything else????

Did I say I know nothing about body work?? Thanks guys. (take it easy on me like you do newbies) hehe

Apply the Ospho and let it dry overnight.
The next day there will be a white dusty residue which can be brushed/blown away, or can be removed with a rag wet with Ospho.
The white residue is a byproduct of the conversion of ferrous oxide to ferrous phosphate.
Using a rag wet with Ospho should not create any more white residue, since there should be no more chemical reaction going on.
After the residue has been removed, I wipe the metal down with acetone, then prime with Rustoleum Rusty metal primer and then final color.
I would not use POR-15 on top of Ospho since it is designed to stick to rusty metal. (I had a total failure from trying that once.) It isn't needed anyway.
Carl

Carl, appreciate the input. I like your way better than mine. I'll get on it first thing next week.

I've had much success with Carl's approach Alvin. I use one of those cup wire brushes on an angle grinder. It will get you down to bare metal. Post ospho treatment depends on the one you use. Some do advise washing down with water to neutralize. The one I use does not. So I just wipe with acetone, let dry and paint. In my experience, almost all rust treatment or metal treatment products use a variant of phosphoric acid to chemically convert the rust, even PPG's metal treatment.

Remove loose rust with a cup brush, blow it off, wipe clean with wax and grease remover, then spray epoxy primer. Best and easiest product process ever invented for bare/rusty metal. No contest!

You will want to THOROUGHLY clean the surface treated with Ospho prior to using epoxy primer. For some reason (probably chemical in nature) epoxy primer and Ospho residue do not get along with each other.
Carl

Ospho will remove paint. Don’t ask me how I know.

Little late response but I used a little different approach with phosphoric acid. I agree that bare metal followed by epoxy primer is best. In my situation, I worked a little bit everyday for 4 years. I body worked each piece one at a time. When bare I scrubbed it with phosphoric acid leaving a lot on the part. Next day I hit it again, this time wiping off all the liquid I could. Stored the parts this way for 1-4 years. Used scotch brite pad to clean before primer.
No rust in between and paint is still perfect 4 years after painting.

I know what you mean. Had a dog that kept knocking over a bottle of Ospho that was sitting in the car port up against the wall.. I would just pick it up and put it back.. one day it happened and it rolled under the front tire of my wife's new '84 Grand Prix.. next morning she left for work not realizing the the bottle burst and the fan blew it all over the front of her car.. by the time I noticed it the next day the paint at the front was ruined! An ounce of prevention would have equaled a pound of cure and $$ had I just put the bottle some place else.



To clairfy POR-15:

Por-15 is designed to be applied over PREPPED rusty metal or PREPPED bare metal, using an item much like Ospo called Por-15 metal prep. If bare metal is sandblasted and rust free, it can be applied direct with no prep.It should never be applied directly over rusty metal or bare metal that has not been properly prepped. People misunderstand this and POR-15 gets a bad rap. Instructions should be followed completely.