Properties of CaO-SiO2 nanocomposites prepared on pure magnesium by using a sol-gel dip-coating technique

A CaO-SiO2 layer was deposited on a pure magnesium substrate that had been prepared by using the spark plasma sintering of atomized powders via a sol-gel process. Various concentrations of tetraethyl orthosilicate (TEOS) were added during the synthesis of the CaO-SiO2 nanocomposites on the pure magnesium substrate; the effects of the TEOS concentration on the corrosion protection and the adhesive properties of the material were investigated. The total thickness of the coating layer ranged from approximately 6 to 10 μm and was affected by the TEOS concentration. Despite the slight surface cracking that occurred on the coating as a result of the strain induced by the annealing process during the deep coating procedure, excellent corrosion and adhesive properties were observed when the TEOS concentration was higher than 15 vol%. When the TEOS concentration was increased to 15 vol%, the corrosion resistance was enhanced, but the adhesive strength was unaffected. Therefore, to produce a CaO-SiO2 coating on pure magnesium for bio-applications, we consider the optimal TEOS concentration to be higher than 15%.