The quest to eliminate rust from the metal of a 1980 Chevy motorhome.
Napa rust dissolving gel and Rust-Oleum semi-gloss protective enamel.
Considering her age, the amount of rust on my Shasta motorhome is about what I would expect. In some areas there's very little, while in others (like the rear bumper at left) the spread is fairly advanced.
This is what I'm starting out with. It's made by Napa and called "Rust Dissolver Gel." I used it once before on the wheels of my Dodge pick-up with limited success. It's corrosive as hell. I had to wear rubber gloves while using it and it seemed to be effective only on the smaller areas of rust. The product's instructions advise liberally coating the affected areas with the gel and allowing it to stand for a minimum of five to ten minutes before washing it off with water. I let it stand for close to an hour and then used cloth rags to rub it into the rusted areas even further, then let it stand another thirty minutes before finally rinsing it off. On my pick-up's wheels, which were only slightly rusted, this dissolving gel was, again, only partially effective. Small rust spots less than half an inch were literally washed off in the water rinse. Larger areas were mostly unaffected. Nowhere on the label's instructions does it say anything about vigorously rubbing the gel into the rusted areas, but I discovered it works quite a bit better when you do.
Following the gel treatment, I'm going to spray all of the exterior metalwork with a white, semi-gloss, protective enamel paint made by Rust-Oleum. Wording on the can makes claim that this product "Stops Rust." That's good. That's encouraging. I suspect that this paint is far better at camouflaging the spread of rust than it is at actually stopping it, but I'm willing to give it the benefit of the doubt for the time being.
...full results to follow...
Well, I finally got a chance to work on the rear bumper of the motorhome over the weekend. I started out with the Napa rust dissolving gel, following the instructions to the letter. It had absolutely no effect on the rust. None. If I'd bought this stuff recently and still had the receipt, I would have already taken it back for a refund. After the failed first attempt I decided to ignore the instructions and apply the gel more aggressively. I coated the entire top of the bumper from end to end with a generous layer of the gel and alternated letting it sit for ten to fifteen minutes at a time and working it into the rust spots with a wire brush. I did this for close to an hour and a half before finally washing the stuff off. End result: No difference at all.
The only option I had left was to get a grinder and grind the rust off. I could grind the bumper down to bare metal and start from there. With a different bumper I might have done that. The spread of rust on this thing was pretty advanced though. In some places there seemed to be as much rust as there was actual metal and the last thing I wanted to do was grind holes in it. Since it was already as clean as it was ever going to get, I decided just to go ahead and paint it with the rust preventing enamel. A before and after comparison can be seen here. Personally, I think it looks pretty good.