The underside of my truck is a little rusty. If I put rustolium on the rust and don't sand it first. Will it help at all or hurt more then help?

 

It will make your wallet lighter. Leave it alone?

 

Is it bad for it?

 

You have get the rust off first, sand then paint

 

I always go under my trucks with a wire brush and sand paper. Wire brush the **** out of the frame, panels, fuel tank covers, (any plates). Use wire brush, and sand paper in crannies. Then I apply asphalt under coat and it's good to go along with some enamel. Could always spray lubricant on it too but I always worry it will wreck the undercoat.

Also spraying oil with diesel everywhere used to be the way to undercoat back in the day.

 

Lock tight makes a product forget the name but its a rust inhibitor...spray can at home depot...works awesome...sprayed my drive shaft and it turned it a blackish color and its been that way for several years now..

 

I think what techrep meant to say was rust reformer. This is the stuff that you spray directly on rust and turns it black. Rust inhibitors are something that you use before there is a problem like brand new metal. This will stop the rust. I work at Home Depot and get asked this question five times a day, first I would use a wire brush on the rust and get all the loose stuff off. After that I would get a 7 dollar bottle of naval jelly. Brush it on with a cheap chip brush that cost under a dollar and let that sit for about ten to twelve minutes no longer than that. It will resolve the rust and as long as it is not rusted through you will be fine. If there is any rust left over after you clean it off then repeat the process. Less work for your arms and it works.