Investigation of titanium oxide doped silane based sol–gel coating for surface protection of aluminium in sodium chloride

Aluminium (Al) plays a vital role in many industrial and engineering applications. But Al undergoes severe corrosion in NaCl environment. The corrosion of metals can be controlled by chromium coating, but the toxicity hinders their applications. Now-a-days sol–gel based silane coatings are considered as best alternative for toxic chromium conversion coatings. In the present study, 3-glycidoxypropyltrimethoxysilane (GPTMS) and 3-aminopropyltrimethoxysilane (APTMS) based sol–gel coatings were prepared to control the corrosion of Al in 3.5% NaCl environment. Further, nano titanium oxide (TiO2) was added with both GPTMS and APTMS to improve the corrosion protection performance of Al in NaCl. The corrosion protection efficiency of the sol–gel coatings was evaluated by electrochemical impedance and Tafel polarization studies. The impedance study suggested that the protection efficiency of TiO2 doped GPTMS and TiO2 doped APTMS are about 97% and 95%, respectively. This work revealed that TiO2 doped GPTMS and APTMS based sol–gel coating protects the Al from corrosion to a significant extent.