How to Paint Over Rust

Mastercoat® will help you paint over rust. We know that painting over rust can be a problematic. In fact, it’s not considered an optimum thing to do. Rather, you should only paint over rust in situations where sandblasting is prohibited or not economically feasible. Painting over rust has long been a tedious, time consuming chore. With Mastercoat® you can apply your paint over marginally prepared rusty surfaces. Mastercoat® stops rust for longer than any competitors’ product.

Founded in 1988, our company wanted to create the most powerful rust sealers and topcoats in the world. We feel with Mastercoat®, we have met and even exceeded that goal. In the past nearly 30 years, we’ve shown that nothing outperforms Mastercoat® in salt spray tests. Our anti‑graffiti subway coating withstood constant washing with solvents and alkali cleaners on NYCTA subway cars. After ten years, the subway cars retained their gloss and color. Mastercoat® is excellent for chassis and underbody protection on any vehicle.

The fact is that most metal rusts at some point especially if it contains even a small bit of iron. Why? The metal will oxidize when exposed to air and moisture. This oxidation is easy to spot. It has a reddish‑brown color and has a tendency to powder or flake off. Rust creates hard bubbles under paint which causes eruptions that can erode the metal and over time the metal can crumble altogether. Use Mastercoat® to protect your metals.

First, you should identify the type of metal you are going to paint. Cast iron, steel and galvanized steel have different qualities and may require different products from our MasterSeries. Next, you should evaluate the environmental conditions where the metal is located. Metal surfaces exposed to the weather face radically different conditions than metal inside a structure. Make sure to choose the correct Mastercoat® for your specific application.

Begin by tackling the rust itself. You should scrape off all the rust you can. Many people use a Dremel to remove rust, debris, and old paint. We suggest that you use a wire wheel and grinder instead. They are more useful than a Dremel tool to get rid of rust. You can also use a hardened metal scraper or shave hook. A shave hook consists of a sharp edged triangle‑shaped steel plate attached to a handle. Do you have stubborn layers of old paint? No problem. Use a paint stripper to eliminate what the scraper missed.

Now, you should sand the metal surface with medium to coarse grit sandpaper. This will get down to the bare metal. You should use a soft utility brush or clean cloth to remove any particulates or remaining abrasives. It is important to work with a clean surface when painting over a rusted area. Our paint and primer will adhere better to the metal this way. The application process will also go more smoothly and result in a cleaner, more professional looking job.  If your metal is dirty or covered in grease of any kind, you should wash the surface of the metal with mineral spirits. You need the surface to be clean before you attempt to paint over rust. That’s why we suggest you use Master Coat metal prep for cleaning the surface prior to using the Master Coat Sealer. You want to put at least two coats of the sealer on prior to painting.

Wait until everything is completely dry. Now, you can begin to paint over the rusted area. Apply several thin coats, making sure that each is completely dry before you add another one. It’s important that you remain patient and allow the paint to dry between coats. Otherwise, you can have problems like bubbling, cracking and wrinkling of the paint finish.

We can provide you with expert technical assistance by contacting us at 1-800-833-8933. To learn more about painting over rust and to check out our entire product line, please visit our website at We look forward to providing you with the materials you need to complete your next paint job over rust.