Aside from barrier coatings, there is another type of corrosion protection coatings that perform a unique function to combat corrosion. These coatings are known as sacrificial coatings, and they are so-called because they contain elements that “self-sacrifice” to the corrosion process, thereby sparing the metal surface from actual corrosion.
The elements in these corrosion protection coatings are commonly zinc, iron or manganese. When sacrificial coatings are applied unto the metal surface, these sacrificial materials lay in wait, and oxidize upon contact with corrosive forces attacking the metal surface. Inorganic phosphate materials are also used in sacrificial corrosion protection coatings, rendering the metal surface impervious to corrosive chemical reactions.
These corrosion protection coatings make the surface resistant to corrosion far longer, because any corrosive reaction involves the sacrificial elements in the coating, and not the surface itself.
A common method of application of sacrificial corrosion protection coatings is using an aluminum or zinc thermal spray. Sacrificial elements such as zinc are melted and sprayed unto the metal surface, settling within the surface profile. The coating system that forms is porous, designed to allow oxidation to take place when corrosive agents are present.
