Evaluation of Corrosion Protection of Sol-Gel Coatings on AZ31B Magnesium Alloy

Magnesium is one of the lightest metals and magnesium alloys have good strength to weight ratio making them very attractive for many particular applications [1]. The main drawback of magnesium alloys is their high corrosion susceptibility. Improving the corrosion protection by deposition of thin hybrid films can expand the areas of applications of relatively cheap magnesium alloys. This work aims at investigation of new anticorrosion coating systems for magnesium alloy AZ31B using hybrid sol-gel films. The sol-gels were prepared by copolymerization of 3- glycidoxypropyltrimethoxysilane (GPTMS), titanium alcoxides and special additives which provide corrosion protection of magnesium alloy. Different compositions of sol-gel systems show enhanced long-term corrosion protection of magnesium alloy. The sol-gel coatings exhibit excellent adhesion to the substrate and protect against the corrosion attack. Corrosion behavior of AZ31B substrates pre-treated with sol–gel derived hybrid coatings was tested by Electrochemical Impedance Spectroscopy (EIS). The morphology and the structure of sol-gel films under study were characterized with SEM/EDS techniques.