Hard anodizing

aluminumfor aeronauticsindustrial

Hard anodizing is a specific application of sulphuric anodizing. This process is usually performed in a bath of sulphuric acid from 10 to 20% (by volume), at low temperature, generally from -5 to 5°C. Description of the process The use of low temperature allows the application of higher current densities (typically 3 A/dm2) and minimizes the dissolution of the oxide, which allows us to reach significant thicknesses (25 to 100 μm), and especially in dense structures. For coatings formed of hard anodizing we note an increase in the hardness, abrasion resistance and electrical and thermal insulation. Consequently, this treatment is particularly recommended when resistance to abrasive or erosive wear is paramount. Colouring and sealing of the coating are possible but they decrease hardness and wear resistance. Appearance: grey or brown (black colouration is possible) Thickness: 5 to 60 µm Microhardness: 300 to 500HV for 50 µm, depending on the alloy Surface condition: slight deterioration of the roughness, Electrical insulation: 500 to 1000 volts~ Coefficient of friction: good under high load Reduction in fatigue: 30 to 50% depending on the alloy Corrosion resistance: - without sealing: ~ 50 h - sealing with nickel salt ~ 300 h - sealing with chromium VI salt ~ 500 h