Effect of silicon on the formation of zirconium-based hybrid coatings on advanced high-strength steel surface

The specific mechanism of influence of added Si in advanced high-strength steel (AHSS) on the formation of zirconium-based hybrid coatings is discussed in detail in this paper. The results of electrochemical impedance spectroscopy (EIS) revealed that the coating resistance of the zirconium-based hybrid coating increased from 11.7 omega center dot cm2 to 359.9 omega center dot cm2 with the increase in silicon content in the high-strength steel from 0.47 wt.% to 1.70 wt.%. The scanning electron microscopy (SEM) analysis demonstrated that the defects within the coating gradually decreased as the silicon content in the high-strength steel increased. Simultaneously, with the increase in silicon content in high-strength steel, the coating resistance of the composite coating increased from 665 omega center dot cm2 to 1544 omega center dot cm2 and the degree of coating damage significantly decreased when combined with bisphenol-A epoxy resin, which indicated that an increase in silicon content in AHSS enhanced the corrosion resistance, uniformity, and adhesion of the zirconium-based hybrid coating. By combining X-ray photoelectron spectroscopy (XPS), glow-discharge optical emission spectroscopy (GDOES) and focused ion beam-transmission electron microscope (FIB-TEM) results, the enhancement of the zirconium-based hybrid coating properties was related to the enhancement of the MnSiO3 and SiO2 contents on the surface of the AHSS. MnSiO3 was found to provide the initial nucleation sites for the zirconium-based hybrid coatings, while SiO2 could accelerate the deposition reaction of the coatings, resulting in the formation of excellent zirconium-based hybrid coatings on high Si steels with higher MnSiO3 and SiO2 contents.