Preparation and Property of Modified Epoxy Resin Chrome-free Docromet Coating

The technology of preparing a chrome-free Dacromet coating with polyurethane modified epoxy resin instead of chromic anhydride was performed. The morphology and composition of the prepared coating were analysed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion resistance of the coating was evaluated by potentiodynamic polarization curve, electrochemical impedance spectroscopy (EIS), ammonium nitrate fast corrosion resistance test and salt water immersion test. The results showed that a dense, uniform and continuous film was formed through curing and cross-linking of resin, which effectively prevented the invasion of corrosive media and improved the corrosion resistance of the coating. The main components of the coating were Zn and Al, when the corrosive medium invaded, the zinc-aluminum powder was passivated to form oxide. The corrosion protection mechanism was mainly the shielding effect, electrochemical action and passivation effect.