About Rust...

[Flatie46]

Ok... there are alot of products that say they stop, prevent or treat rust. Some even say they turn it to a paintable primer without much more than a quick bushing with a wire brush to remove the loose scale. Products like POR15 and Chassie Saver you can coat over the rust and as advertised "stop it" or kill it. How do they do this? Does anybody know what the magic chemical is that stops rust? For years I have done amature bodywork being very careful to sand, blast or cut out every bit of rusted metal to keep it from spreading. I had learned that most primers are porus and if used without paint on top would cause rust. At first I thought POR 15 would not let air or moisture in and the rust couldn't continue. I guess there's more to it than that. Could anybody shed some light. I've been debating this with a fellow car nut and he's got me scratchin' my head.

[48mirage]

A mild phosphoric acid will stop the rusting. It turns the iron oxide to ferric phosphate, it's a kind of pickling process.

[Flatie46]

A mild phosphoric acid will stop the rusting. It turns the iron oxide to ferric phosphate, it's a kind of pickling process.

So is this what's in the POR15 and Chassie Saver? When the rust is turned to ferric phosprate it is then to a point it can't reasonably turn back?

[PatS....]

POR15 claims to stop rust by sealing out oxygen, but even a tiny pinhole will negate that claim.

Rhinoliner and most other spray on boxliners do a better job of sealing out oxygen.

[JerseyHarold]

I've read that POR-15 is a moisture-cure urethane product, so it acts as a sealer rather than a chemical converter.

[Joe Flanagan]

As others have said, POR-15 works like a barrier. Zero Rust is the same thing. I prefer it over POR because it's easier to work with. POR has a very hard, glossy finish that's hard to beat, though. Phosphoric acid will eat away rust and neutralize what is left but you still have to get something over it. I get my phosphoric acid at Home Depot in gallon jugs. You can dilute it with water and use it as a bath for derusting small parts.

[JerseyHarold]

If you're not in a hurry, you can use white vinegar as a de-rusting bath. Actually works pretty well.

[Flatie46]

How well does paint stick to POR15? I'm wanting a flat look in the area's I'm going to apply it. Is there any prep?

[48mirage]

Naval Jelly is the most common form of the phosphoric acid for addressing rust.

[GaryPrice]

and Camaros, in the floorboards, and in the vent/cowl of one. It won't stick to smooth surfaces. It has to be roughed up or etched. They have a pre-treatment, which is a phosphiric acid spray, that neutralizes the rust, and the paint then seals it. The one cowl area I did, there wasn't much way to pre-treatment, so I painted it directly on the rust. I painted the entire floorboard, which was pitted badly and had a few pin holes in it, plus one hole about as long and wide as my index finger. With three coats, the pin holes sealed well. The paint covers very well. A little goes a long way. After treating and painting the floors, I soaked some fiberglass mat with the paint, and laid over the hole, then one more coat on that area. I also painted over the hole and fiberglass mat from underneath.

Afterward it was as solid as new. I could jump up and down on that floor and it didn't give. I had that car for five years before I finally got it painted and the drivetrain/interior etc. and I never had any of the POR paint peel or rust poke through it.

The other cars I've done, one hasn't been done long and the other is in progress now, so I don't have a track record on them. On the first one though, it lasted as long as I had the car, and the cowl was good also. So the jury's still out on them.

One of my friends liked the looks of my floors so well, he had me help him do the trunk of his Nova. It was similar to my floors. Heavily pitted with one hole about half dollar size. We treated it the same, and then we used the POR primer. POR paint doesn't stick very well to slick surfaces. They have their own primer that's supposedly "formulated" to stick to it. I'm sure there's probably other primers that are cheaper that will work. All the paint and primer were brushed with sponge brushes, same as I've done all mine. After the primer, my friend sprayed his trunk with the GM speckled paint. It looked great. That was seven years ago and, although he sold the car locally, it's still

holding up great and has won a couple of times at Super Chevy.

I'd never put it on a part that shows, or try and use it anywhere that has structural support. For floors, trunks, cowls (not Fred Flinstone), until I have a bad experience, I'll continue to use it.

[1940_dodge]

If you're not in a hurry, you can use white vinegar as a de-rusting bath. Actually works pretty well.

You know, how does that work? I've heard a couple people saying 4 parts vinegar to 1 part water and other methods of mixing the vinegar properly. Do you dilute it at all?

[TodFitch]

You know, how does that work? I've heard a couple people saying 4 parts vinegar to 1 part water and other methods of mixing the vinegar properly. Do you dilute it at all?

Using an acid, even a mild acid like diluted vinegar, to strip rust will probably also eat good metal.

I personally like the electrolysis method. Faster than mild acids and less damaging to parts. Chances are you already have the battery charger, a plastic bucket and some scrap metal to use as sacrificial electrodes. All I had to get was some old fashioned washing soda as all we had in the laundry area was new fangled enzyme and/or oxi type boosters. And, from what I've read, there is nothing toxic to plants in the waste solution when you are done so it is easy to dispose of.

[Eneto-55]

I've read of people using molassas for de-rusting as well. (Not sure if that was on this forum, or another.)

Regarding use of acids, if you match the acid to the metal being derusted correctly, the acid will not eat the metal itself. (For instance, aluminum in muriatic acid will literally "boil" the acid until the piece is completely eaten up. Nitric acid will do the same for steel, if I remember correctly.)

I have heard people say (years ago) that leaving steel in an acid (like phosphoric) may cause a change in the tensile strength of the metal, that is, steel may become less maleable, or more brittle. I have never read this in a source I know to be realiable, nor did I ever hear it from anyone at the plating shop where I worked for some years (back in the 70's & 80's). So I would actually like to know if this is true, if there is anyone here who knows for certain. But then I've also heard people say that sand blasting will also do the same thing, so I don't know what to think.

Neto

Edited January 30, 2012 by Eneto-55

[Young Ed]

. And, from what I've read, there is nothing toxic to plants in the waste solution when you are done so it is easy to dispose of.

I had read that too and I dumped 2 buckets of solution on my lawn throughout last summer. The grass didn't die.

[JerseyHarold]

You know, how does that work? I've heard a couple people saying 4 parts vinegar to 1 part water and other methods of mixing the vinegar properly. Do you dilute it at all?

I've just dunked smaller parts in undiluted vinegar (the kind you buy in the supermarket) and the rust dissolves off the part. The vinegar gets a brown discoloration to it as the process progresses.

You have to monitor the part to make sure it doesn't get eaten away while it's dunked. The only mishap I had was many years ago. I was derusting a kids' bicycle chain and forgot about it for a couple of days. When I pulled it out of the vinegar, the chain literally fell apart because the link connectors eroded too much.