1. . 
Any thin material, liquid or powder, which, applied over a structure, forms a continuous film to protect against corrosion. Corrosion coatings should possess flexibility, resistance against impact and moisture, good adhesion and cohesion, and chemical resistance to the exposure conditions (such as temperature, hydrogen sulfide). Organic coatings such as polyethylenes (plastic) are normally used for external protection of pipelines while asphalt and coal tar enamels are used to protect buried pipes or undersides of oilfield tanks. Inorganic coating such as zinc-silicate is used to protect drilling and production platforms above the splash zone and nickel phosphate coating is used to protect packer body parts.
See: coating flaw