Home Improvement : Three Means of Dealing With Rust : Removal: It can be done with abrasion or chemical treatment. Or it can be neutralized with other chemical products.
When it comes right down to it, there are three basic ways to deal with rust. You can remove it via abrasion. You can attack it chemically with a rust remover. Or you can leave it right where it is, but chemically transform it into something else. Each of these techniques works, but each is best in certain situations.
Rubbing away rust with abrasion isn’t a lot of fun, but it can certainly be effective, taking you right down to bright shiny metal and producing a surface that is ready to prime and paint. For most homeowners, the best tool for this job is a disk sander. You can also sand the area by hand. Start with 80- or 100-grit paper to chew away major deposits and smooth out any pits. Then go to 220 to prepare for final painting.
A sandblaster is another very effective abrasive tool. It’s main advantage over a sander is its ability to work into the spots, creases or highly textured surfaces the disk sander can’t conform to or reach.
What about wire wheels and cups? They can conform to unusual shapes better than a disk sander, but aren’t as effective as abrasives at getting right down to bare metal.
A relatively new product (shown in the sketch) I’ve tried actually combines the flexibility of the wire wheel with the clean finish produced by abrasives. The secret is nylon bristles impregnated with abrasives. The bristles conform nicely to contoured work, and the abrasives cut right down to bare metal.
Chemical removers work pretty well, but ironically, not if you follow the directions. These read more like a sales pitch than helpful advice: “Just brush on, let set and wash away rust like magic!”
Don’t believe it. I use a somewhat more labor-intensive procedure. First, since rust is often impregnated with grease, oil, grime and other contaminants that tend to seal it against rust removers, I like to start with a thorough cleaning. Scrubbing with a strong dishwasher detergent usually does the job.
Then, I turn to the rust remover. Most of these contain phosphoric acid, which eats away at the rust. Since this is a chemical reaction, it will proceed faster if you work where it is warm.
Whenever possible, I like to soak rusted parts in a tray or bowl of remover, stirring them around every few minutes. This keeps the rust wet and constantly exposed to fresh remover.
You can’t very well put a car fender in a tray of remover, however. So for large work, I brush the stuff on as thickly as possible, then go back every few minutes and brush on some more. This keeps the rust constantly in contact with fresh remover.
For really tough rust, you may have to help the process along by rubbing with sandpaper or steel wool. If you do this, wear rubber gloves. Then let things soak. A couple of hours isn’t too long.
Finally, wash off the remover very carefully with detergent and water. If you cut corners on this step you’ll probably end up with a white dusty coating all over the work.
In some cases, it pays to follow up with a wire wheel to knock off any deposits still clinging to the metal. If you plan to paint, it’s a good idea to sand lightly with 100- then 220-grit paper.
Chemical transformers are the latest weapons against rust. Yet, they don’t remove it at all. Instead they chemically transform it into a blue/black compound that binds well to the base metal beneath it, and at the same time protects against further rust.
These transformers--sold under brand names such as Neutra-Rust, Rust-Oleum, Rust Reformer and Extend--are easy to use and effective. If you like the look of the blue/black surface they produce, you can leave it as is. It needs no further treatment. If you will be happy with a so-so paint job, you can also paint right over these treatments without the need to prime.
But since these treatments don’t actually remove rust, they can’t produce a nice smooth surface ready for a high-gloss paint job. Of course, if you do want a smooth finish, you can sand the rust after it has been treated, but if you are going to do that, you might as well skip the chemical treatment altogether and rely completely on a thorough sanding.
It’s your choice, but if you do decide to use a reformer, you can go ahead and follow label directions. Unlike rust remover instructions, these are right on the mark.
Once you’ve dealt with rust, you may want to put down a protective finish. This consists of one or two coats of primer, followed by the desired top coats. I usually use aerosol primers. Alkyd-based primers (such as Rust-Oleum) are tough and work well over existing finishes, but are slow to dry.
Lacquer primers (like Krylon and most auto touch-up aerosol primers) dry much faster, but they may attack existing finishes already on your work. Test them on an inconspicuous spot if possible.
For the smoothest final finish, spray on at least three coats of the final color. Let each coat dry and sand lightly between coats with 320 wet-or-dry paper. Use 400-grit paper before the final coat. If your work isn’t that critical, just brush on your top coat and go fishing.