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 Ω·cm² to 359.9 Ω·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 Ω·cm² to 1544 Ω·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.