Influence of zirconium-based conversion treatment on dry and wet adhesion of carbon steel-fusion bonded epoxy coating systems

摘要

In recent years, the industrial demand increased to develop a viable eco-friendly conversion treatment for a wide cariety of metal substrates and applications. In this development it is crucial to understand the effect of a possible treatment on subsequent adhesion and interfacial bonding of coating systems. The object of this research was to investigate the effect of a zirconium-based conversion treatment on interfacial bonding and adhesion of fusion bonded epoxy coating on mild carbon steel. Delamination of epoxy coated carbon steel surfaces was analysed with scanning Kelvin probe (SKP) in order to study the kinetics of delamination growth away from a coating defect. In situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was used to probe electrolyte diffusion towards the hidden epoxy-carbon steel model interface. The ATR-FTIR provided information about the interfacial chemistry changes and with electrochemical impedance spectroscopy (EIS) the diffusion of ions through the coating and the corresponding coating degradation was measured with time. Corresponding EIS on the epoxy coated carbon steel surfaces were shown to be in good agreement with the ATR-FTIR model system. Peel-off mechanical testing showed the zirconium-based conversion treatment can improve dry and wet adhesion of the epoxy coating to carbon steel surface significantly.