Effect of La3+ on corrosion behavior of Zn-Fe alloy coating in sulfuric acid solution

The effects of Lanthanum ions on the corrosion behavior of Zn-Fe alloy coating in acid corrosion solution，which was electroplated on the surface of A3 steel substrate with various electrolytes of Lanthanum salt，were investigated. The corrosion behavior of the Zn-Fe alloy coating was studied by the Linear sweep voltammetry and AC impedance in the 020 mol·L-1 sulfuric acid solution at 30 ℃. The microstructure and shape of Zn-Fe alloy coating before and after corrosion was studied by XRD and SEM. The results indicate that the addition of lanthanum salt decreases the grain size of Zn-Fe alloy coating and retains the preferred orientation of Zn-Fe alloy coatings, but affects the intensity of diffraction for crystal planes. When 090 g·L-1 La2(SO4)3 is added in the electrolytes, the coatings of Zn-Fe alloy are more uniform and compact, and the electrocrystallization appears layered. The Jpp and Jp of Zn-Fe alloy coating are reduced evidently, Rp is increased, and the Zn-Fe alloy coating has better corrosion resistance.