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Wet Weather Coats

© John J. Pascarella

Although it doesn't seem very long ago, several years has gone by since we talked about nails. In that article (Don't Bite Your Nails), we covered the different styles of nails and their uses. I briefly mentioned special nails, such as galvanized. This time around, I want to take a closer look at nails that can be used in outdoor applications or where water and moisture may cause regular nails to rust. There are three basic types of nails that will resist the corrosive effects of moisture: galvanized, aluminum and stainless steel.

First, let's look at galvanized nails. A coating of zinc helps keep the nail from rusting by corroding instead of the iron nail itself. The chemical changes that occur when iron reacts with water is called oxidation. The oxygen in the water reacts with the iron to form iron oxide, or rust, which is very brittle. The zinc coating of a galvanized nail reacts with the oxygen instead of the iron, forming zinc oxide, which is stronger than the zinc by itself. So as the galvanized coating corrodes, it becomes stronger and more able to resist further corrosion. The protectiveness of the galvanized coating does not last forever, however. Eventually, a galvanized nail will rust, but it does take quite a bit longer than uncoated nails. When buying galvanized nails, look for "hot dipped" nails, which have a thicker zinc coating on them.

Galvanized nails are the best choice for most outdoor building. But if you are planning to use either cedar, redwood or pressure-treated building materials, don't use zinc coated nails. These products react chemically with the zinc and will noticeably shorten the life of the nail. Another application where you don't want to use zinc coated nails is when you are installing copper flashing. The copper and zinc, together with a little water, create the same electrical reaction that you find in using copper and galvanized iron plumbing parts (see Don't Sweat the Little Stuff). This electrical reaction will quickly corrode both metals.

Aluminum nails are perfect for working with cedar, redwood and pressure treated lumber. The aluminum doesn't react with these woods like zinc coated nails will. And while aluminum is a much softer metal than steel, these nails have been hardened to make them almost as strong as steel nails. They come with different designs on the shank to resist pulling out. A couple of the best holding shank types are the twisted and the ring shanks.