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Oxidation

Shock absorber pistons also undergo nitriding and oxidation processes.

The oxidation process, which can be done at three different temperatures, is also known as steam tempering in some sources.

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It is done in a chemical solution at 140-150°C, in a salt bath around 350°C, or in water vapor at 530-550°C.

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The main purpose is to create a controlled oxidation film on the material surface. The output of this process is usually 3-5 µm thick iron(II,III) oxide.

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It is often applied after nitriding and nitrocarburization to provide corrosion resistance to the material. Depending on the type of material, 100 hours of resistance can easily be achieved in salt tests conducted according to ASTM B117.

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It is done to prevent liquid metal adhesion in metal injection molds. All other applications are generally for corrosion resistance. It is used for parts such as drill bits and milling dies to increase both the beautiful appearance and the oil retention ability of the surface.

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Benefits of oxidation,

  • Better corrosion resistance

  • Impressive black surface

  • Improved wear resistance

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The materials it is applied to,

  • Automatic steels

  • Heat Treatable & Construction steels

  • Hot work tool steels

  • High speed steels

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