Formation and characterisation of zirconium-based conversion coating on steel

Zirconium-based conversion coating (ZrCC) was successfully prepared on the samples of cold-rolled steel from the solution of H2ZrF6 and HNO3 at controlled pH. Its surface morphology was analysed by the 3D optical microscope and scanning electron microscope. Its chemical composition and structure were investigated by energy-dispersive X-ray spectroscopy, X-ray diffraction analysis and X-ray photoelectron spectroscopy. The open-circuit potential measurement was used to study the coating formation process, and the electrochemical impedance spectroscopy test was employed to analyze the behaviors of the coatings prepared at different deposition time. According to the analysis results, the deposition mechanism of ZrCC on steel was proposed, and the chemical schematic diagram was also designed. The corrosion resistance performance of ZrCC with cathodic electrodeposition primers was also evaluated by salt spray exposure of 1000 h.