Like anything in nature, metals are subject to deterioration if not properly protected. Metals may deteriorate due to rust and corrosion, abrasion, wear, and chemical agents. The only method to combat this deterioration is the use of metal coatings, which is, essentially, painting the metal. What should be known about particular metal coatings and their application depends on the specific end use of the metal to be coated. Metal is designed to withstand stress and strain for extended periods, thus, protecting metal enhances its effectiveness.
When deliberating metal coatings, protection value should be the first consideration. Certain coatings' formulations are designed specifically to protect metal from rust and corrosion, as well as contamination from chemicals and dirt. This is a controlling factor in marine environments, for heavy construction vehicles, for trains, aircraft, and automotive applications. Weather conditions, petroleum-based lubricants, fuel spills, grime, and dirt will all take a toll on unprotected metal.
Some metal coatings are applied as lubricants, or as torque agents. Screws, bolts, and fasteners are among the metallic items coated for lubrication and torque, effecting ease of unscrewing or tightening. In most cases these items are either coated with water-based inorganic coatings, or electroplated where the finished texture and color are of somewhat secondary importance.
Resistance to abrasion and impact is another factor to be aware of when contemplating metal coatings. A protective coating will often resist the scratching and chipping that can result from the use and occasionally necessary abuse of metal equipment and devices. Generally, these coatings are a bit more flexible than others, able to withstand considerable impact and movement.
Finally, appearance, or finish, may be a high priority in the application of metal coatings. Is color a consideration? Texture? Opacity? Protection and lubrication are very important, but appearance of the finished product should also be kept in mind. This is especially true for automotive and aircraft metals, where a rough finish measurably disturbs the aerodynamics of these machines. Of course, color is especially important in automotive coatings. Pleasing to the eye can be, after all, of equal importance as longevity and fuel economy.
Metal coatings are applied in a variety of ways, and using a number of formulations and vehicles. Cost, therefore, is always a factor, as is timeliness of application and curing. Metal may be sprayed with either liquid or powder coatings. It may be dipped into a coating formulation, or electroplated, all in addition to numerous other methods. In summation, each coating application and formulation is designed to produce a coated metal in varying time frames, at more or less expense, and varying levels of thickness, appearance and effectiveness.