How can I fix rock chips in my car's paint job?

I have a 2009 Hyundai Elantra that has suffered a few rock chips on its paint job. I bought some touch-up paint and would like to cover over the affected areas; however, I noticed that some of these chipped-off areas have rust starting to form in them. If I cover it over with the touch-up paint now, the rust will continue to spread anyway, won't it? These chipped-off areas are so small I am not sure of the most effective way of removing the rust before applying the paint. Also, I purchased the rust-protection feature when I bought my car brand-new, so why would rust be forming in the first place? – Carol in Vernon, B.C.

Demon rust – I know it well. Rust is the creation of red oxides when iron or its alloys combine with oxygen and water or moisture. The presence of salt, even if only in the air, speeds up the process.

For iron to become iron oxide, three things are required: iron, water and oxygen. Steel, the material used for the vast majority of automobile panels and structures, is an alloy of iron with a tiny bit of carbon.

It is common for auto makers to demand that the steel they purchase from suppliers be galvanized – covered by a thin coating of zinc. This provides a layer of protection preventing the iron (steel) beneath from the moisture and oxygen necessary to create rust or iron oxide.

So much for chemistry, on to reality. In order for rust to appear, any layers of protection have to be compromised, whether they be the thin coat of zinc, the primer and various coats of paint, the clear coat of paint applied atop the colour coat(s) or any rust protection on top of that.

The most common ways for these multiple layers of protection to be penetrated are 1) drilling a hole to apply a piece of trim or for some other reason, 2) repairs to crash damage or rock picks.

In your case, the rock picks have negated any protection provided by the rust-proofing and proper repairs will involve thorough cleaning to a point below where the oxidization has occurred with subsequent protection applied immediately.

Once oxidization has begun, it eats beneath the surface of the metal making it difficult to eradicate. For small areas like a rock pick, use a very sharp instrument to get to a fresh surface and a layer or two of primer, followed by as many layers of colour as necessary to reach the surface of the factory paint.

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