Environmentally Friendly Protective Cycles for Aluminum Components for Marine Applications

Marine propulsion systems must be protected from corrosion degradation. In particular, in the case of aluminium alloys parts, a protective cycle consisting in a surface pretreatment and an organic coating layer is often applied.
Traditionally chromate based pretreatments are often applied on aluminium alloys in aggressive environments for the protective ability of chromate layers, together with the self healing and adhesion promotion ability. The toxicity of chromium hexavalent is pressing to find new environmentally friendly solutions.
In this paper new results concerning different protective cycles were presented. New surface pretreatments, including zirco-fluotitanates and chromium III treatments, were characterized in conjunction with different organic layers, as waterborne paints, powder coatings and electrodeposited organic coatings. All the systems are free from organic solvents and toxic active pigments.
By electrochemical measurements and salt spray exposure it was possible to optimize the protective cycle with low environmental impact for the protection of aluminium components for marine propulsion systems, proving final performance comparable with the traditional systems containing chemicals with high environmental impact.