rust reformers

I'm curious about rust reformers. I've used Rust-oleum Rust Reformer in the spray cans and Harbor Freights Rust Reformer. Rust-oleum appears great--it eaves a nice flat black finish, but I'm certain it has black paint in with the acids that do the "reforming". So it makes me wonder if it really worked or just covered up the rust with paint. Harbor freights certainly doesn't have any paint in it. It goes on clear and well this is what I just don't get--sometimes it turns the rust black really good as it dries and sometimes it just makes the rust look glossy--same can mind you. It appears some pieces of metal it works on and some it doesn't. I was spraying it on some of the rusted spots where the paint is sheeting off my JD 755 and it did nothing but make the rust look glossy. It wasn't badly rusted just surface rust. I sprayed it on some trailer hubs tonight--cleaning them up a bit before putting some new wheels on and after a bit of time to dry they were solid black. Again not bad rust just surface rust over the center of the hub, the lug bolts and nuts. Any ideas?

Taking that a step further, these new (to me) wheels are pretty chrome on the outside and quite rusty with some chrome on the inside. I sprayed it on the inside of them too--2 coats on one of them and I ran out of reformer. I noticed when they dried it'd dried into a film that flaked of the chrome parts--not surprising it didn't stick to chrome. The rust was partly black and part not. Given this film however I have to figure this stuff contains a sealer in with the acid. So if I was to go back tomorrow with a new can and respray the wheels to hopefully get the remainder of the rust converted would that work now that tonight's coat has dried on it?

Trying to figure all this out--thinking seriously about buying several cans and spraying the whole trailer--it's rust colored. I don't have the time to wire brush it or the money to sand blast it.

I'm also considering Rust-oleum's brush on rust converter which I hear is clear and turns black like the HF stuff. I read that is really good--see link.
Comparative Study of Commercially Available Rust Converters

Some years back I was a fan of the rustoleum with the copolymer. I found that it didn't last if not top coated. Then I tried the POR-15 metal prep which is basically phosphoric acid which converts rust to inert iron phosphate. That holds up better. Now I am using Rust Mort by SEM it is basically phosphoric acid, and goes on watery thin. It turns the rust black and somewhat glossy. You need to rinse in or with clear water because excess will turn white.

In the reforming process there is a chemical change taking place. The chemical change is what turns the surface black. Rust, which is iron oxide has the oxygen replaced by the phosphate in the restorer. You end up with iron phosphate rather than iron oxide. NO paint is used to give the black color.

I just go straight to the source and use phosphoric acid.

They sell it at Home Depot, it's cheap. Find it in the paint area - gallon jugs of green stuff. Think it's labled metal prep or something like
that.

put some in a spray bottle.

Smells like rotten eggs once it starts reacting.

Just paint right over it once it dries.

(obviously get rid of loose rust first - no treatment is going to do any good if there's layers of rust that don't get touched.

has worked very well for me on anything I've restored.

Exactly right! A gallon will do about four old rusty tractors.

Thanks to both of you. I will.

A followup--I understand it's used as a concrete etcher too thus I wouldn't want to do this on my concrete floor--not a problem. I'd prefer to do this in the driveway--does it hurt asphalt? I can hose it down good after finishing but that might mean some spray on it for a few hours. I could do it in the yard but I'd suspect it would kill grass. I figure I'd brush it on or spray it with and old spray bottle.

(quoted from post at 08:38:19 06/19/15) Thanks to both of you. I will.

A followup--I understand it's used as a concrete etcher too thus I wouldn't want to do this on my concrete floor--not a problem. I'd prefer to do this in the driveway--does it hurt asphalt? I can hose it down good after finishing but that might mean some spray on it for a few hours. I could do it in the yard but I'd suspect it would kill grass. I figure I'd brush it on or spray it with and old spray bottle.

Click to expand...

Brush it on. While phosphoric is not a very bad acid it is still corrosive, and not good for your lungs, so you don't want to atomize it.