Property characterization and formation mechanism of anticorrosion film coated on AZ31B Mg alloy by SNAP technology

Self-assembled nanophase particle (SNAP) technology was use to protect AZ31B Mg alloy. The SNAP sol was synthesized in an aqueous solution by the organosilanes of 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraethoxysilane (TEOS), the crosslink agent of triethylene tetramine (TETA). Structure, thermal stability and corrosion protection of SNAP system (including SNAP sol and SNAP film on the Mg substrate) were studied by various complementary techniques. The results demonstrated that the nanoparticles in the SNAP sol suspended stably for 3–4 months during the process of the hydrolysis reaction; for the crosslink reaction, a large silica network structure was formed by the addition of TETA. Moreover, the properties of thermal stability, compactness and corrosion protection of the SNAP system increased obviously by crosslink reaction. Bonding mechanism of the SNAP film/Mg system showed that the improved properties were due to high degree of cross linking of Si–O–Si network structure, high density of Mg–O–Si bonds and high content of inorganic component.