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HARD ANODIZING

HARD ANODIZING TYPE III

Hard anodized coatings on aluminium and its alloys are formed during the process of electrolytic oxidation in acid electrolytes, under accurately adjusted conditions of temperature and electric current. The coating is formed in such a way that a half of its thickness penetrates into the parent material and the other half builds up externally.

When compared to conventional anodized films the coatings formed during the process of hard anodizing are much thicker, which demonstrate much better resistance to wear. Depending on the type and condition of the base material the achievable thickness of hard anodized films may range from 25µm to 250 µm.

Colours of hard anodized coatings depend on types of the base material and thickness of the built-up film. Generally, the colours include various shades of brown and grey. With very thick coatings it is also possible to achieve black colour of the film.

PROPERTIES OF HARD ANODIZED COATINGS

  • Very high resistance to wearing and abrasion.
  • Perfect resistance to corrosion (1000 to 1500 h in a saline chamber).
  • Excellent hardness (380 – 550 HV 0.025).
  • Optimum antifriction properties.
  • High resistance to electric breakdown (1500 V at the film thickness of 50 µm).
  • Insensitivity to high temperatures (up to 2000ºC at short-term expositions).
  • Excellent properties of thermal insulation (1/10 to 1/30 of thermal conductivity demonstrated by the base material).

TYPICAL APPLICATIONS FOR HARD ANODIZED COATINGS

  1. Pneumatic and hydraulic cylinders
  2. Pistons
  3. Injection moulds
  4. Valves
  5. Nozzles and injectors
  6. Belt pulleys
  7. Chirurgical instruments
  8. Toothed transmission gears
  9. Heating plates
  10. Household kitchenware (frying pans, pots)
  11. Automotive industry
  12. Avionic industry

INFORMATION FOR CUSTOMERS

With submission of an order for the service of hard anodizing the following details must be specified:

  1. The alloy the workpieces are made
  2. Target hardness of the alloy
  3. Required thickness of coating
  4. Possible locations of electric contacts
  5. Technical drawings of workpieces (if available)

NOTE: When type of the alloy and its condition are specified incorrectly, the treated workpieces may get damaged.