Improved corrosion protection of aluminium alloy AA 2024 by sol-gel hybrid coatings after surface pretreatment by silanisation

摘要

Sol-gel derived organic-inorganic hybrid coatings have been investigated as a potential replacement for the environmentally hazardous chromate conversion coatings for corrosion protection of aerospace aluminium alloy AA 2024. Sol-gel hybrid coatings were prepared using a sol mixture (1:1 volume ratio) of 3-glycidoxypropyl trimethoxysilane and tetraethoxysilane and doped with cerium nitrate and deposited on AA 2024 by dip coating and spray coating techniques. The effect of surface pretreatment on the corrosion protection efficiency of the sol-gel hybrid coatings was studied. The corrosion resistance of the coatings in 3-5% sodium chloride solution was evaluated by potentiodynamic polarisation measurements, electrochemical impedance spectroscopy and salt spray tests. The results showed that a sol-gel coating system with a simple silanisation as surface pretreatment exhibited improved corrosion protection for AA 2024.