What is Hard Anodising?
Hard Anodising (Hardcoat) is an electrochemically produced layer of aluminium oxide on the surface of aluminium. A controlled thickness can be obtained from just a few microns up to 120 microns depending upon the alloy used.
The process is used to produce much thicker, harder and corrosion resistant coatings than the Sulphuric Acid process. The thickness can be very closely controlled, and the cool operating temperature of the process prevents thermal or physical distortion of precision engineered parts or equipment.
Secondary treatments such as impregnation with solid film lubricants and coloured dyes are available.
We are founder members of the International Hard Anodizing Association.
Hardness & Wear Resistance
The wear resistance of the coating is closely related to the surface finish. The rougher the surface finish the more likely under high local pressure, for the coating to break away in minute particles and get trapped or impinged into the sliding surface, hence causing an abrasive medium. The surface finish of the component should be better than the final finish required as the hard anodising process increases the surface roughness. Where a fine finish is required, honing or grinding is recommended.
The properties of the hard anodised aluminium as a bearing material are good and are improved by impregnating the coating with lubricants such as “NITUFF®”.
Hard Anodising is a cost-effective choice for wear and corrosion resistant surfaces on aluminium alloys. Abrasion resistance can be equal to that of tool steel or hard chrome around 1,000 VPN, with the actual hardness of the Hard Anodised film up to 350-500 micro Vickers Hardness. The process is environmentally beneficial due to the chemicals used and its low cost for recycling.
The number of applications for Hard Anodised aluminium continues to grow, and any manufacturer or user of engineering equipment should contact us to discuss whether hard anodic coatings could profitably and advantageously replace existing parts.