A waterproof coating is a substance or material made to coat an object or surface and prevent it from suffering any negative effects from exposure to water. Waterproof coatings are used in many different situations and by many different professions. Construction workers and craftsmen may use some form of waterproof coating, such as waterproof paint, stain, acrylic polymers, or oils to prevent wood, cement, or metal from suffering the effects of exposure to water. Many individuals use waterproof materials to cover their portable electronic devices, as they are often expensive and can be damaged easily as a result of contact with water. A waterproof coating project can be conducted by professionals or by amateurs with the proper supplies.
Water can damage different substances and surfaces in different ways based on the particular manner in which the water molecules interact with the surface. Wood tends to be very porous, allowing water molecules to saturate wooden surfaces and cause them to decompose and rot. Metal, on the other hand, is often oxidized by the oxygen present in water or in the air; this process tends to be much more rapid in the presence of water, especially salty or acidic water. The oxidation of metal results in rust. When portable electronic devices such as music players and cell phones are exposed to water, the internal electrical parts can short out, rendering the devices useless.
A waterproof coating is made specifically to handle the specific threat that water poses to a given substance. A waterproof coating for wood, such as some forms of paint or stain, is made to fill and block the pores in wood so water can not get inside. Coatings for concrete and cement work similarly. A waterproof coating for metal is usually some kind of adhesive, oily substance that repels water, preventing it from ever actually touching the metal. Plastic or rubber cases or coverings are generally used to prevent electronic devices from sustaining damage from water.
There are several more exotic methods of protecting some substances, particularly metals, from the effects of water. Galvanization is one process used to protect steel or iron from rusting. The steel or iron is coated with a thin layer of zinc, which oxidizes much more readily than the metal it protects does. This is a "sacrificial" method of protecting the metal — all of the zinc is oxidized before the iron or steel can rust.