High performance reaction-induced quasi-ceramic silicone conversion coating for corrosion protection of aluminium alloys

Regulations posed by the Environmental Protection Agency on the use of chromate conversion coatings have triggered the need to find alternative materials for the corrosion protection of aluminium and its alloys. A simple four-step process of creating a quasi-ceramic coating has been developed. The coating, which is made of environmentally safe chemicals, should be easily and safely manufactured for bulk production. Here, we describe the synthesis, characterization and evaluation of a silicone conversion coating for aluminium metal and its alloys. The spectroscopic techniques utilised in this study have shown the mode of the bonding mechanism between the metal and the coating. Thermal analysis of the material was conducted to evaluate its stability, while nano-mechanical properties were determined and correlated with the surface morphology of the coating. Results obtained from FTIR and XPS spectroscopic techniques suggested that the coating adhered to the metal substrates through active surface functionalities, and thermal analysis showed that the coatings contained volatile solvents including water that evaporated at lower temperatures. Nano-mechanical tests suggested that the coating had elastic properties. Accelerated corrosion and immersion tests were also performed on coated and uncoated aluminium alloys. Coated and uncoated aluminium alloys were also exposed to soil containing sulphate-reducing bacteria. Coated coupons showed excellent corrosion protection and antifouling characteristics indicating that the coatings were impervious and of high integrity. Published by Elsevier B.V.