ALUMINIZING

Aluminizing is a high temperature process where aluminum vapor diffuses into the surface of the base metal forming metallurgical aluminide alloys. The aluminizing process inhibits corrosion protection to the surface of steels. This is a metallurgically bonded process ( diffused) to the base metal. Stainless steels and nickel alloys are ideal for the process. The process is very effective to stop or slow down corrosion in high temperature environments. It’s also effective in resisting the effects of oxidation, sulfidation and carburization.

Aluminizing and thermo-chemical diffusion process are carried out at high temperatures, typically in the range of 750–1100°C with a defined time at temperature dependent on the substrate material  to create a diffusion potential.

The surface of materials is normally treated to protect it from the external  environment. The process improves corrosion resistance at elevated temperatures which then also improves oxidation resistance and wear. The composition of the coating can be modified to suit the application. In some cases the part can be platinum plated first to improve the corrosion resistance. This is typically done on Areo and Aero derivative turbine blades. Aluminizing is a thermo-chemical diffusion treatment where in the surface layer of the material is impregnated with aluminum. It is primarily used on steels, but also on nickel and cobalt based alloys to obtain greater creep resistance, hardness and corrosion resistance.

The aluminizing process is usually operating at a relatively high temperature of 750–1100°C with pre-determined times at temperature to produce a diffused layer into the substrate from the surface. There are several methods to do this process  however slurry and vapor are more convenient processes

Aluminizing Properties:

  • Sulfidation resistance – steel protection from H2S, SO2, SO3 attack.

  • Oxidation resistance – stable aluminum oxide film formed.

  • Carburization resistance – prevents carbon diffusion into base metal.

  • Hydrogen permeation – diffusion rates of H2 into steel reduced.

  • Masked surfaces of aluminized components can be welded.

Photomicrograph of the aluminized structure

Aluminizing Applications:

  • Gas turbine components
  • Automotive turbo charger components
  • Boiler components
  • Oil and gas industries