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Rust is the sworn enemy of all things metal. Horrible oxygen intrusion will destroy even the most carefully laid sheet metal. This is particularly problematic with older cars. My ‘82 Mercedes 300TD is a good example. It has 250,000 miles on it, and is in wonderful shape. However, the body is beginning to deteriorate. Eventually rust will attack and destroy critical structural elements and no rebuilt transmission or flawless engine will prevent it from being junked. However, if rust is caught early it can be slowed or stopped, adding many years to the car, and preventing the purchase of yet another new automobile.

POR-15 is a product designed specifically to help fix rusting metal. Unlike most paints, POR-15 is a moisture curing epoxy that, when painted directly onto rust, will suck the moisture out of the rust and seal it up, preventing further growth. Traditional paints just trap the moisture, letting the rust continue unhindered and out of sight.

Continue reading for a picture-heavy description of the process.

Using POR-15 is best done in four parts, removing existing paint and loose rust, cleaning the surface, prepping the surface chemically, and finally applying the POR-15. Not all of these steps are required for all applications.

Here is some rust on my Mercedes’s driver’s side front fender. Someone put some touch-up paint over it, but the rust has continued to grow underneath, spreading outward and bubbling the paint. The whole car needs a paint job, so in this case we will just be removing the rust and sealing the damage so that body filler can be applied without worrying about trapping moisture.

You can use any abrasive tools to remove loose, flakey rust, and existing paint. I chose a power drill with the two abrasive wheels, and a small abrasive brush from my dremel tool. Wire brushes are handy as well. Remember that the goal is not to remove all the rust, but to remove the crumbly surface rust. POR-15 bonds very well to rusty surfaces, and in fact is meant to do so.

Here is the surface with all of the surface rust and surrounding paint removed. I’ve gone down to clean metal in some areas, and in others left the hard rust alone. The goal is a rough surface that the POR-15 can bond to securely.

The surface must be very clean for the POR-15 to properly adhere. Use a good water soluble degreaser such as Marine Clean, a POR-15 product. In this case I diluted it with 3 parts hot water and sprayed it onto the surface. I rinsed well with clean water, and patted dry.

For rusty metal it is best to prep the surface with POR-15 “Metal Ready”. Metal Ready consists of Phosphoric acid and Zinc phosphate. These chemicals remove rust and coat rusty areas in a layer of zinc, which makes a perfect surface for the POR-15 to adhere to. This step also helps prevent future rust. Apply the Metal Ready directly to the surface with a brush, and wait 10-15 minutes. For heavy rust, wait up to 30 minutes. Use clean water to completely rinse the Metal Ready off after the time is up. Then pat dry.

POR-15 comes in a paint can that is a real bitch to open. But keep at it, and you’ll get to the goods. Mix well until the POR-15 is completely blended. Do not shake, it will work bubbles into the mixture which you do not want. After mixing, pour or scoop a working portion of the POR-15 into another container. Work from this container with a foam-style brush to apply a thin coat of POR-15 to the surface. Once the coat has become tacky, in 3-5 hours, apply a second coat. You may continue to apply coats to build up the surface if necessary.

After dispensing your POR-15 into another container, you must seal the original container immediately by placing a layer of plastic wrap over the container, and then pressing the metal lid back on. If you omit this step, the POR-15 will cure in the can, and seal it closed forever. Always keep the POR-15 sealed, and reseal the can as quickly as possible after mixing and dispensing.

After you have applied at least two coats of POR-15, you are done! It is recommended that you apply a traditional paint over the top of POR-15 because UV radiation will discolor POR-15 (though it will not compromise its protective abilities. You can also apply body fillers over POR-15, or sand it smooth. I chose the Silver POR-15 for two reasons, it matches my car better, and it contains metal fillers which help it to fill holes and bridge gaps. POR-15 comes in several colors, including black and clear as well.

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