Left untreated and in contact with certain chemicals, steel can rust. Rust, or ferrous oxide, occurs when iron elements oxidize. When rust overtakes a steel nail, it causes corrosion and can leave unsightly stains on wood materials. For that reason, the steel nails you buy at the hardware store probably aren't naked, or untreated.
Most nails have undergone one of three types of coating processes:
- Galvanizing: steel nails coated with zinc particles to resist rust formation
- Bluing: nails heated to form an oxidized surface layer for added strength
- Cementing: nails covered in resin to increase the friction between them and the building material
[source: Forest Products Laboratory]
When it comes to rust resistance, galvanized nails are the most effective. These work well for outdoor applications that could subject nails to moisture and rain, as well as corrosive chemicals in treated wood. Zinc arms nails against rust because it's more reactive than iron and therefore oxidizes more easily. That way, the zinc forms zinc oxide and protects the metal below.
The galvanization process takes place via electroplating or hot-dipping. In electroplating, nails are doused in an electrically conductive solution and zinc. The reaction of the steel with the solution binds the zinc to the nail to form a thin layer [source: Bliss]. The primary disadvantage associated with electroplating is inconsistency; the zinc particles may not cover the nail uniformly, degrading its overall quality.
Many carpenters opt for hot-dipped nails over electroplated ones when dealing with wood materials. Hot-dipping involves submerging the nails in molten zinc, thus covering them more evenly. Some hot-dipped nails receive two zinc washings, in which case they're referred to as double-dipped. Essentially, the thicker and smoother the amount of zinc coating, the better the nail will avoid rusting.
In addition to warding off oxidation, hot-dipped nails also have improved staying power. The coarse zinc particles cling more tightly to whatever they're being hammered into. Consequently, they perform well for attaching parts of house trim, decks, stairs and window frames [source: Locke and Locke].
Moreover, hot-dipped and electroplated nails hit on only a fraction of those on the market. So before you pull out the hammer or nail gun, first consider the appropriate nail for the job.