Sol–gel coatings of low sintering temperature for corrosion protection of ZE41 magnesium alloy

Silica coatings have been obtained through the organic sol–gel route on magnesium–zinc alloys (ZE41) using low sintering temperatures for their corrosion protection. Tetraethoxysilane (TEOS) was used as alkoxide precursor, and the coatings, monolayer and 3-layers, were deposited by dip-coating technique at a controlled extraction speed of 35 cm/min. Temperatures of 135 °C were applied for several hours for coating densification avoiding mechanical deterioration of the magnesium alloy. To optimize the corrosion behaviour of the coatings different concentrations of sol solution were investigated. The corrosion resistance of the different coatings were tested by immersion in 3.5 wt.% NaCl aqueous solution and by electrochemical corrosion techniques. Low temperature silica coatings provided corrosion protection for up to 7 days without degrading the mechanical properties of the magnesium alloy used.