Influence of DETA on Thermal and Corrosion Protection Properties of GPTMS-TEOS Hybrid Coatings on Q215 Steel

Abstract

High-performance coating could be used to protect steels in engineering. The GPTMS-TEOS hybrid coatings were successfully prepared using (3-glycidoxypropyl) trimethoxysilane (GPTMS) and tetraethylorthosilicate (TEOS) as reaction raw materials and diethylenetriamine (DETA) as both a curing agent and catalyst at room temperature. The hybrid coating contained amorphous SiO2 and was characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The DETA content of the hybrid coating has a significant impact on the performance of the coating. As the DETA content increases, the thermal stability of the hybrid coating increases at 400–600 °C due to the production of more SiO2 in the amine-rich state. However, the gelation time decreases dramatically, preventing the hybrid coating from better infiltrating the surface of the steel substrate. In addition, there are not enough silicon hydroxyl groups to bond with the hydroxyl groups on the surface of carbon steel and adhesion is significantly reduced. Therefore, hybrid coatings with a moderate DETA content (NH:epoxy ratio equivalent to 1:1) show the best corrosion resistance, with a third-order magnitude increase in corrosion resistance compared to that of carbon steel.