Chromic Acid Anodising
This process produces relatively thin coatings in the order of 2.5 microns which tend to be opaque or semi-opaque in appearance and less wear resistant but more corrosion resistant than sulphuric acid type coatings of equal thickness. As chromic acid does not attack the base aluminium it is safe to use on components where the electrolyte may be trapped in joints and crevices and is the preferred method for castings.
Applications & Uses
Chromic acid anodising is used primarily in the aircraft, ammunition and the Automotive industries, also where very tight tolerances need to be maintained. It is the recommended process for casting due to the chromic acid being inert to the base aluminium. The coating is also recommended where excellent bonding is required, also for grain adhesion properties and in conjunction with the best corrosion resistance in paint schemes.
Properties Of The Film
- Thin coatings
- High corrosion resistance
- No loss of the fatigue strength of the aluminium
- Excellent bonding properties
- Excellent adhesion properties
- Preferred process for castings and fabricated components
- Excellent crack detection method for casting
- Showing grain flow characteristics of forging