Corrosion resistance of lamellar aluminium pigments coated by SiO2 by sol–gel method

The aluminium pigments were coated with SiO2 by sol–gel method to improve their stability. The effects of formulation factors, such as medium of reaction, adding sequence of catalyst and number of coating, were investigated. The stability of the coated aluminium pigments in acid was examined by measuring the hydrogen generation amount. It was found that the coating layer formation is due to the condensation of tetraethyl orthosilicate (TEOS) to form a dense 3D cross-linked layer on the surface of aluminium. The optimized sequence of adding catalysts would be hydrochloride first, then ammonia. Stability tests confirmed that the aluminium pigments have better corrosion resistance after coating with SiO2.

Research highlights
► 1-butanol is the best medium of reaction in the sol–gel processing.
► The catalyst hydrochloride should be added prior to ammonia in the process.
► Triple-layer coatings show higher quality on corrosion resistance than single layer.
► TEOS formed a dense 3D cross-linked layer on the surface of aluminum with increasing time.