Thermal spray coatings are widely used in preventing corrosion of many materials. A common application is the use of zinc to protect iron substrates. In this method, the surface of the metal is prepared by abrasive blast cleaning to ensure it is cleaned and roughened. Zinc wire (99.95% pure) at a controlled rate into a arc spraying process and the atomized metal impinges upon the surface being coated and becomes bonded to it. This process is easily adopted to production environments. Thickness variable will generally 100-120 um but coatings of upto um can be applied. Metallizing is considered a cold process in that the aluminium or zinc is deposited onto steel by spraying rather than by dipping the steel into a bath of molten zinc as with galvanizing. The steel remains relatively cool at about 250 degree – 300 degree F. There is virtually no risk of heat distortion or weld damage by Metallizing.
No size or shape limitations very economical for work with high weight to area ratio. Uneconomical on open mesh. Access difficulties may limit application (e.g. Inside tubes). Best method of applying very thick coatings.
Coating with sealants that can provide a base for paints to give long life structures.
The ability to control the coating thickness and superior adhesion of the zinc to the iron substrate.
All metals have properties that cause them to react as on anode or a cathode when coupled to another material in a corrosive environment.
The application of zinc (anodic coating) to iron substrates forms a protective layer and results in a corrosion protection referred to as cathodic protection or sacrificial protection. The Substrate iron becomes the cathode and the zinc coating becomes the sacrificial anode.