Chromate Replacement in Aluminium Corrosion Protection Coatings

摘要

A major field of activity in surface finishing deals with corrosion protection of Aluminium surfaces. Currently, the Aluminium surfaces are zincated and chromated prior to the final galvanic or paint coating. In other applications, the aluminium surface is hard or decorative anodised, respectively. Chromating fulfils several functions, such as corrosion protection and paint adhesion. Since chromates are being banned, alternatives have been developed. The main issue is an environmental friendly replacement with remaining performance and quality. Functional coatings based on polysiloxanes, which result in organic-inorganic hybrid coating systems provide a vast variety of properties, which may be tailored as required. Some of these properties include excellent corrosion protection together with high mechanical stability and / or abrasion resistance. In most cases a consecutive coating (paint, lacquer, powder coating) is beneficial, which implies that the adhesion to the following layer system is possible. In this work both, a topcoat and an interfacial coating system based on polysiloxanes were developed and characterised.