Electroplating Al Coating In Molten Salt And High Temperature Oxidation Process

The phase, morphology and properties of electroplating aluminum coating on Q235 steel after being oxidized at different temperature have been investigated by means of XRD and SEM, and the hardness, adhesion and corrosion resistance of aluminum coating have been tested. The results showed that:The minimum of critical current density (I_pp) and passivated current density (I_p) of electroplating aluminum coating appears in 180g/L H2SO4 solution. With the increment of H2SO4 concentration, the breadth of passivation region increases.Electroplating aluminum coating on Q235 steel after being high temperature oxidized at 500°C and less, the electroplating aluminum layer is composed of Al phase, can't appear new phase. And being oxidized at 700°C, Al₅Fe₂ phase appears. With the increment of oxidation temperature, the porosity of the electroplating aluminum coating decreases.The hardness of electroplating aluminum coating on Q235 steel after being high temperature oxidized at 300°C is similar with no-treated electroplating aluminum coating. But at 500°C, the hardness of the coating increases. It increased obviously from 93HV_0.05 of no-treated to 225HV_0.05 when the temperature is 700°C, the rate of increment is 142%.The adhesion of the coating and Q235 steel just increased obviously when the temperature is above 500°C.With the increment of oxidation temperature, the passivated current density (I_p) decreased firstly and increased later, the minimum appeared at 500°C. Critical current density (I_pp) decreased obviously , passivation region breadth increased continuously and more kept constantly over 500°C So the corrosion resistance, characterized by anodic polarization curve in...