Investigation of microstructure related to corrosion evolution, mechanical and electrochemical properties on doped Si of binary Zn-Al coating

The cycling corrosion test is the first evaluation for silicon doped of 55 wt% Al-Zn coated (GL) steel and microstructure related to corrosion evolution, mechanical and electrochemical properties on the GL steel is investigated. Native oxides grown on the GL surface were hydrolyzed to form the hydroxide, followed by the formation of the hydrozincite and layered double hydroxides products. Galvanic corrosion selectively occurred at the boundary Zn-rich phase to form simonkolleite. These corrosion products played a role in GL protection. We clearly expressed images that the pitting morphology began to occur at the boundary Zn-rich region and stopped corroding on the Fe-Al intermetallic compound layer. Following this, the primary Al-rich region started to be corroded until GL corrosion finish, then red rust of steel corrosion occurred. Moreover, we were the first to study that the tensile surface by bending could accelerate the GL corrosion at the intersection of the boundary phase; in contrast, the compressive surface inhibited corrosion slightly. Electrochemical impedance measurements combined with an equivalent circuit model were developed to support specific corrosion evolution.