Process Anodizing & Hard-anodizing
Decorative anodizing is used for corrosion and wear resistance, for achieving a uniform and smooth finishing, for colouring, and for facilitating adhesion of paints and lacquers.
Thickness: 5-25 micron.

Hard-anodizing is used for technical purposes: against corrosion and wear, for electrical insulation, and, by impregnating the surfaces with teflon particles, for achieving low friction.
Thickness: 50-100 micron.

The aluminium part is placed in an electrolyte (commonly of sulfuric acid) and used as anode. Due to electrolytic oxidation a protective aluminium oxide layer forms on its surface, which becomes very hard and scratch resistant.
Danish Name Anodisering & hårdanodisering
Category Surface treatments, Electroplating
Materials Substrates:
Aluminium oxide (coating)
Typical products Piston
Window frame panel
Zoom lens
References AHC Oberflächentechnik
Arbeitsgemeinschaft der Deutschen Galvanotechnik
Dansk Anodisering Industri ApS
Galvanisk Kompagni A/S
Galvano Wernigerode GmbH
Environmen- tal notes Anodizing is an environment-friendly process, relatively safe. No extraordinary precautions are needed to ensure worker safety, only a minimum of special protective clothing.
Additional info For colour anodizing electrolytes contain organic acids, and special aluminium alloys determine the colour. Many colours are available.

Hard-anodizing uses the same principle but lower temperatures (0 C) and higher current densities.
Photo Thomas Nissen (Computer graphics)
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