Coatings - heat and oxidation resistance
 

These are coatings which improve the high temperature performance of a substrate. These coatings should resist high temperature chemical or physical dissolution, mechanical damage because of erosion, or both.

Coatings resistant to oxidizing atmospheres
These coatings must protect a substrate which could otherwise fail because of oxidation at high temperatures. The coatings must:

1. Resist oxygen diffusion from the atmosphere
2. Resist rapid diffusion of itself into the substrate
3. Have a melting point above the operating temperature
4. Have a low vapor pressure at operating temperature. Resistance to mechanical action is not a requirement.

examples: conveyor in ovens, heat exchanger, chimney's, smoke duct, etc.

Coatings resistant to corrosive gases
These coatings must protect a substrate exposed to corrosive gasses at high temperatures. Both oxidation and chemical reactivity must be considered. Gases tend to react with the coating, preventing formation of protective adhesive oxides, or forming friable compounds of penetrating to attack the substrate. Resistance to mechanical action is not a requirement. However some of these coatings will resist erosion better than others
Examples: piston heads, exhaust valves, combustion chambers, etc...

Coatings resistant to erosion above 1550 F
These coatings must resist high temperatures and also particle erosion. High velocity particles and high pressure gases at high temperatures constitute a severely destructive environment. These coatings must resist wear caused by sharp, hard particles which are moving.
Examples: jet engines, after burners, turbine parts,etc...

Coatings for thermal barriers
These coatings have low conductivity, and act as thermal barriers to prevent the base metal from reaching its melting point. They also function through ability to transfer radiation.
Examples: dipping tanks, conveyors, cooling fins, moulds, etc.