I'm soon to embark on de-rusting several places on the Barth. I'll claim a modest degree of expertise in dealing with rust, so I'll pontificate on my procedures.

Dealing with rust breaks down into several elements:

1. Removal of rust
2. Chemical neutralizing of non-removable rust
3. Applying a chemical barrier to rust
4. Applying a physical barrier to rust-inducing compounds

First for the DeRust Crusader is the removal of as much rust as can be done. No matter how efficient one is, all the rust can't be removed. There's a theory that one can seal in the rust and it'll no longer be a problem, but that's what one gets when one crosses an alligator with a large sausage - a "Croc of Baloney".

So after physically removing as much rust as possible, the next step for the DeRust Crusader is to chemically neutralize it. There are many effective treatments on the market, and since they seem to be regional, I'll not go into brands, but what the DeRust Crusader is looking for is a phosphate primer (not Naval Jelly, which is virtually worthless to the DeRust Crusader) that will convert the rust to a phosphate salt. This does two things. First, the rust is chemically neutralized, so it can no longer operate as a breeding ground for more rust. Secondly, the effective rust-neutralization primer creates a non-porous barrier to the things that promote rust. But, for the DeRust Crusader, that's but a beginning.

After the rust-converting primer is applied and allowed to fester for a day, then the DeRust Crusader removes as much of the resulting scale/mung mechanically and with a strong solvent (lacquer thinner or acetone) as possible. A second or third coat of the acid primer may be needed as the residue is removed.

Stage 3 sees the DeRust Crusader applying two or three coats of Cold Galvanizing Spray. This inhibits, chemically, future rust.

But the cold galvanizing spray merely operates to neutralize Demon Rust that tries to re-emerge.

What the DeRust Crusader wants to do is prevent the cold galvanizing spray from having to awaken. Step 4 provides an additional layer of protection by sealing off the cold galvanizing spray from attacks, and it's epoxy spray paint.

Fergit Rust-O-Leum - it ain't got what it takes, despite the claims; this isn't a knock, but many paints tend to be porous. Epoxy is much less so.

So the DeRust Crusader says, "Go forth and slay corrosion! May The Force be with you!"

Rusty,

Regional shouldn't be an issue that keeps you from disclosing information. What products are/will you use? I going to be working on the rust in some of my compartments this summer.

Bill G

I use Ospho by Skybryte Chemicals, or Phos-Go by TheoChem. Both are green. What's needed is a phosphoric acid primer, not a plain "rust-remover". I apply it with a dish mop (looks likea wad of strings with a handle - the sponge ones don't hold up well), throwaway (bristle, not sponge) paint brush, or hand spray bottle.

There are several cold galvanizing sprays on the market; my preference is Krylon, followed by Rust-O-Leum. I don't recommend Dupli-Color, because I've had the valve stick shut on a couple of cans.

I generally use Ace Hardware Black Appliance Epoxy. For interior (like basement storage compartments), any automotive Dove Grey.

I've used most of the products Rusty speaks of. Ospho & cold galvanize work well, but my preference is "Extend" rust treatment.

It appears to be phosphoric acid in a latex base. It goes on milky, dries clear, except on rust where it turns black. It must be painted if exposed to weather, and isn't suitable for body panels that require a smooth glossy finish. It's available in aerosol cans, or a brushable liquid.

It requires the same prep, as the other stuff, but takes one less step to finish, as it serves as it's own primer.

Like most products, it works best if you follow the directions.

I've heard good things about POR15 as well, but never tried it.

Ospho is a primer, the same as Extend, although I've never used the latter. The cold galvanizing coats are to provide extra (chemical) protection.

Sometimes one coat of Ospho is sufficient, but where the rust is deeply embedded, the top scale after treating needs to be knocked off and more Ospho applied. In those places the phosphoric acid is depleted before the rust is, or it couldn't penetrate to the deeper rust pockets.

Never heard of POR15 until now...

I still have some Ospho from the last time I used it several years ago. Maybe the formulation has changed, but what I have is watery & thinner than the Extend. I was not confortable without further priming after I used it.

I always try to get my exposed surfaces clean of rust before I start to finish them, so I only have to treat the pits. I've had to knock off scale occasionally, but always managed to get down to some bare metal.

POR15 has been advertised for several years in automotive magazines. There was an extensive discussion of it in this forum a year ago, or so, & I recently saw a display in my local NAPA store. The sample looked like porcelain, (POR ?) but I suspect it's pricier than other treatments

I like the Ospho because it is thin and will penetrate. Years ago I talked to the owner of TheoChem, as he had released a phosphoric acid-containing cleaner that did a remarkable job on truly cruddy gelcoat. We also talked about the PhosGo "primer", as I wanted to used it on my boat engine (phosphoric acid primers were new back then). He said he called it a "primer" to signify that, unlike Naval Jelly, then popular for rust removal, it didn't have to be washed off. He did recommend a primer over his primer after a mineral spirits/lacquer thinner/acetone wash, to remove any of the PhosGo that hadn't been activated by contact with rust.

I use the cold galvanizing spray as the second primer, and it's served me well.

IMHO, POR-15 is garbage. They church it up like some kind of miracle coating but the black stuff I tried oxidized like mad, and came off like flying woodchips if you hit it with a pressure washer. I'll admit my prep work was sub-par and prep is important, but Tremclad works better than POR-15 and is cheap and I've had acceptable results with lazy prep work. Stick with the recommendations of Olroy and Rusty, or use a good quality 2 part automotive topcoat with a primer/sealer.

quote:

Originally posted by modeleh:
IMHO, POR-15 is garbage.

Didn't do much for me, either. I even had rust come back on some gauge bezels that were not heavily rusted at all. I think it is a very hard paint that does nothing to treat or neutralize corrosion. Plus it sets up in the can.

The only positive thing I have heard from anyone first hand was from a fellow who had a problem with his birds eating paing off the cage. The POR 15 stood up better than other paint. I know a number of guys who use it on their hot rods and collector cars, but they baby their cars so much that anything would be OK by them.

Some of our ocean boat owners here like CRC Rust Arrest. I find it interesting that its listed ingredients include Oxalic and Tannic acid, instead of phosphoric or other acids.

Oxalic and tannic acid do remove rust, but they don't convert the rust to a usable base for protecting. In other words, what's left is bare metal, which can start rusting right away.

I found two places that suggest an approach for parts that can be removed from the coach.

I'm going to give this a try with the engine V-belt pulleys, aluminum or steel new ones of suitable quality are very expensive. If it works out maybe a few other parts.

Has anyone used this approach?


http://antique-engines.com/electrol.asp

http://www.rowand.net/Shop/Tools/Electrolysis.htm

Oh yea laundry / washing soda, what the heck is this stuff?

The web site says "washing soda is Sodium Carbonate (Na2CO3), baking soda is Sodium Bicarbonate (NaHCO3), and borax is Sodium Tetraborate Decahydrate (Na2B4O7*10H2O), all different chemical compounds."

Well it is clear it is not TSP.

Baking soda I know about but when it comes time to do the wash I just dump in the contents of what ever brightly colored box or bottle Lana has next to the machine.


Let's say this works, ok now what primer is most effective? Clearly the rust killer primers are not needed, or are they?



Thanks:

Timothy

This actually works (although using most battery chargers is a bit dangerous - I'd use a battery then disconnect and recharge it).

Electrolysis does indeed remove the rust (to bare metal - which then immediately starts oxidizing again). Electrolysis breaks up the Fe3 O2 (ferric oxide) molecules into free iron and oxygen (which is expelled as a gas). Some of the water is broken down into hydrogen and oxygen molecules, which is why the outgas is very explosive.

Phosphoric acid does the same thing chemically - the phosphor ions displace the oxygen in the rust (which causes the bubbles you see).

For very heavily rusted items, elctrolysis is an effective way to remove large deposits of rust. While it removes the existing rust, it doesn't prevent future rust.

An acid treatment is still needed to inhibit the rust which will start immediately upon the part's removal from the electrolyte.

The advantage of electrolysis is that it removes the rust a bit more elegantly than mechanical means. The advantage of an acid primer is that it converts the rust to a phosphate salt that's non-porous, and provides a physical barrier to oxidation in its own right, so it'a a one-step process.

I haven't use electrolysis in a while, but I'd use acid primer afterwards before proceeding any further. Cold galvanizing spray over the acid primer is another preventive measure (the zinc in the primer is a sacrificial anode, chemically protecting the iron).

Then I use the epoxy (or urethane) paint on top as an additional physical barrier.

However, if the V-belt pulleys are pitted in the groove/s, I'd recommend replacement, otherwise (I speak from experience, here - saved $70, got to replace a belt after 600 miles in the rain outside Nashville - and had to clean up the crankshaft pulley anyway as well) they will chew up belts very quickly. If any idler pulleys are rusted, I'd get a whole new assembly, as the bearings are suspect.

I'll go one step farther on safety.....Do this outside, and have both yourself and the charger upwind. I did this a long time ago on an old gun. Rusty is right about instant re-rusting.

I think Rusty just likes phosphoric acid because it smells like peach cobbler.

Never much of a fan of peach cobbler, but Ospho is tasty over brekfast cereal...and you don't have to wash the spoon...

On of my neighbors just painted some patio rail with Zero Rust and had some left over he didn't want to pour back into the can. So he offered it to me.

Well, my steps are blistering and rusting under their paint, and I have been planning to remove them for sandblasting, peaches and painting. Now, with no time before the paint set up, I knocked all the loose paint and flaking rust off with a disc sander and applied the Zero Rust. I even painted my freshly-rusted new genset exhaust.

My neighbor swears by this stuff on his railings, and we are a mile from the ocean, so there is a lot of salt in the air.

So, in a few years, I will have a report.

Anyone else know anything about this stuff? Their site makes it look pretty good. I do notice they sell a phospho peachy prep for really rusted stuff.