Aluminizing

Definition - What does Aluminizing mean?

Aluminizing is a high-temperature chemical vapor deposition (CVD) process whereby aluminum vapors diffuse into the surface of the base metal, forming new metallurgical aluminide alloys.

The aluminizing process protects the base material from corrosion in elevated temperatures. Aluminizing is used extensively by industry to protect steel components and structures from heat oxidation and sealing at service temperatures up to 10,000°C, ensuring long-term protection.

Corrosionpedia explains Aluminizing

Aluminizing or aluminum diffusion alloying is an economical process for inhibiting corrosion by protecting the surface of steels, stainless steels and nickel alloys operating in severe high-temperature environments. Similar to the galvanizing process, aluminum is metallurgically bonded to the steel surface, providing excellent heat reflectivity and corrosion protection.

Aluminizing or diffusion of aluminum into the surface of the steel or alloy helps slow down or stop corrosion by protecting the surface in corrosive and/or high temperature environments. It is also very effective in combating the effects of sulfidation, oxidation, and carburization.

Aluminizing has following 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.

For example, steel that has been coated with an aluminum-silicon alloy, known as aluminized steel, resists corrosion and heat better than the base steel material. Aluminized steel is used industrially for high-temperature applications such as in burners or ovens. This material is also used to make pipes that will carry corrosive materials, such as steam or acids. Aluminized steel is used in everyday products such as cookware and outdoor grills, as well. Aluminized steel exhibits superior corrosion resistance compared with galvanized steel, but typically costs more.

Aluminum is preferred for its lightweight, anti-corrosive and thermal conductivity properties, whereas galvanized steel is heavier and more expensive. Aluminization has superior performance compared to galvanization for resistance to atmospheric, salt spray and muffler condensate corrosion.

Aluminizing is particularly effective for protecting mild, low alloy and high carbon steels. It is very effective at protecting generator chimneys, ducts, generator mufflers, and boiler chimneys against heat and corrosion at high temperatures. Spray aluminizing is particularly advantageous in marine and acidic environments. The aluminizing coating is particularly resistant to attacks by sulfurous gases. Using aluminizing, especially in petrochemical processing equipment and gas plants, is advantageous.

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