In order to investigate the law and mechanism of selective oxidation of Quenching and Partitioning (Q&P) steel under different annealing parameters, the sensitivity of alloy elements added in Q&P steel to the annealing parameters was explored. Galvanizing experiments of QP steel were carried out at different annealing temperatures(770 °C and 730 °C) and different holding times(180 s and 300 s). The concentration change of selective oxidation element and the alloying element distribution in the coating were analyzed by Glow Discharge Optical Emission Spectrometer (GDOES), the morphology of surface oxides and inhibition layer were observed by Scanning Electron Microscope (SEM). The results showed that higher annealing temperature(770 °C) and longer annealing time(300 s) could both increase the concentration of Mn and Si on the surface of Q&P steel, improve the oxidation degree of steel surface, thin the inhibition layer, and lead to more leakage plating and deterioration of surface coating quality. The Mn depth profiles showing a parabolic trend and reaching its maximum value at about 20 nm below the surface, while the concentration of Si gradually decreases from the surface to the interior. The selective oxidation of Si and Mn are more sensitive to the annealing temperature than the annealing time.

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The galvanizing experiment of QP steel was carried out in two different concentrations of hydrogen content (5% and 15%) with the aim of revealing the mechanism of different hydrogen content on the selective oxidation of high strength QP steel. The morphology of oxide and inhibitory layer on the surface of steel plate was observed by SEM, and the distribution of alloying elements on the surface and coating was characterized by GDOES. The results show that higher hydrogen content makes the environment more reductive, changing the iron oxide on the surface into active iron that can react with liquid zinc. As a result, the enrichment of Si and Mn on the surface is generally reduced, the compactness of the inhibition layer is reduced, the exposed area of the steel plate surface becomes larger, and the amount of leakage decreases.