Ecological prepaint treatment of aluminium alloys

Abstract

The preparation of aluminium alloys before painting is fundamental to achieving good coating adhesion and superior corrosion resistance. A number of well defined surface treatment techniques have been acknowledged as accepted practice throughout the global industry. Chemical based treatment methods have included the use of proprietary alkaline cleaners, acidic phosphates and hexavalent chromium based chromate solutions. Many of these have become objectionable due to the increased regulation of hazardous materials, growing restrictions on waste discharge and the need to remain competitive through process cost reduction. New technologies are now entering the market as ecological alternatives to these traditional chemical treatments. These include the adoption of bioremediated cleaners, the application of organic dry in place coatings and the use of chromium free passivate films. Despite the current global economic difficulties, it is imperative that industry continues to develop its 'green' credentials because applicator experience has shown the adoption of latest technologies produce tangible benefits such as waste minimisation and improved process efficiency, at a reduced cost while achieving similar coating performance.