Are there any inexpensive rust inhibitors?

[Chaz]

The epoxy primer I spoke of is about 120.00 for 2 gallons.

[gus]

Walmart sells latex based Rust Converter in the auto body repair/paint section in small bottles, about 8/16 oz as I remember. It is not cheap by the gallon but large quantities will not keep unless used up quickly.

The only thing I've used that works goes by many names but it is all latex based which means it can be cleaned up with water before it sets up. After it dries it forms a very hard black crust over rust. It can be painted or not, doesn't seem to make much difference. There must be rust for it to work, it will not work on bare metal.

I used Naval Jelly for many, many years and it is nothing but a big pain - and it doesn't last.

Once I found this stuff I quit looking. Some of the newer names may be better, but I doubt it, and they are very expensive.

I use it on rusted battery boxes and fittings, the only thing I've ever used that stops that rust cold.

If it doesn't say it is latex based and makes a hard black crust I don't buy it. It is very thick and is easily applied with a brush or small roller. It also comes in spray cans but can thicken and become unusable in a short time. Wear gloves, it burns the skin and will burn into concrete floors, but is easily washed off with water.

Rustoleum never worked for me and a test by Consumer Reports said it didn't work any better than plain paint. Maybe it has improved, but I gave up on it long ago.

[belfert]

Okay, I'm getting a bit off my own topic.

I'm slowly dismantling the trailer to see the extent of the rust.  Areas in front of the wheels have almost no rust.  I suppose the back got road spray from the wheels in the winter.  There is only one place that needs metal welded in so far, but I know the front needs a bunch of welding work.  I wanted to get more panels off this evening but rain and mosquitoes chased me inside.

I suspect my plan of Rustoleum will work considering most everything will be covered up by aluminum skin.  I would like to use Rust bullet, but the extra cost and time I just don't want to invest in this thing.

[gus]

If you fasten steel to Al the best thing to use between the two is Zinc Chromate paint.

[belfert]

It turns out that any part of the frame the customer can't normally see was not painted at all.  I was wondering why some parts of the frame were rusty when they were covered with aluminum.

My new aluminum skin is painted on both sides so I am not worried about corrosion between the dissimiliar metals.  The old skin corroded from road salt, not from the steel frame.

[gus]

Brian,

I admire your optimism, but Al and steel connected will rust, it is just a matter of time. Normal paint will not stop this, the fasteners themselves are a path of corrosion. No matter which fastener you use it is not compatible with one of the metals. All it takes is dirt and/or water.

If you use aircraft type anodized fasteners they will sacrifice themselves by rusting and saving the base metals.

Again, Zinc Chromate primer between the two metals will make the best barrier you can use.

Rust converters are only useful where there is already rust.

[rv_safetyman]

Brian, looks like you have talked yourself out of sandblasting.  I really don't like sandblasting on assembled parts.  The sand gets into every crack, nook, and cranny and can destroy any rotating parts.

A few years ago, I would have recommended PPG DP40 as one of the best two part epoxy primers.  It was the best product on the market as far as I was concerned (had a lot of technical contact with PPG folks then).  However, it has been compromised and is now DP40LF (lead free).  Still a pretty good product, but not near as good as the "old days".

Gus, you sent me on a search.  I had been told that Zinc Chromate was no longer available.  Turns out that is not correct.

It was used in military aircraft in WWII.  I think it was mandated on old tube style planes (allowed inspectors to carefully check the frame, as it was a very thin, somewhat translucent coating).  Great stuff then.  I wonder how much it has been "watered down" today?

I found one source that looks like they have something very close to what I call the (old) formula:  http://www.aircraftspruce.com/catalog/cspages/ptizincchromateprimer.php

Jim

[gus]

Jim,

I buy almost all my aircraft stuff from AirSpruce, very good company and will do anything to keep a customer happy. I do get my ZC spray cans from them. I think it comes in cans for brushing but it is much easier to apply the correct amount with a spray can.

It is still widely used by light aircraft mechanics, mostly for small repairs, because nothing else does what it does. Don't know if it has been reformulated, but probably has, almost everything chemical has.

It was used in all aircraft for years, the military used thick coatings of dark green. Never knew why, probably because it cost more!! I always use a thin coat of the light yellow translucent stuff to avoid dark holes back in airframes, makes for easier inspections.

Epoxy primers are used mostly now for fabric covered aircraft steel airframes because it isn't affected by the fabric coatings.

Good point about thin coating, it is not supposed to be put on thick like other primers. There is a chemical reason for this but I forgot it after all these years. I do know it does the job. I think it has to do with allowing the metal to breath, but don't quote me on that!