La^(3+)对Zn-Fe合金镀层耐蚀性能的影响

Effect of La^(3+) on Corrosion Resistance of Zn-Fe Alloy Coating

在A3钢表面Zn-Fe合金电镀液中加入镧盐,研究La^(3+)对Zn-Fe合金镀层在酸性介质中腐蚀行为的影响。用线性扫描伏安法和电化学阻抗法,研究Zn-Fe合金镀层在30℃的0.20mol/L H_2SO_4溶液中的腐蚀行为。用XRD和SEM研究Zn-Fe合金镀层在腐蚀前后的微观结构和形貌的变化。结果表明,加入镧盐没有改变Zn-Fe合金镀层的晶面择优取向,但影响各晶面衍射峰强度,使镀层结晶粒度变小;当加入La_2(SO_4)_3为0.90 g/L时,Zn-Fe合金镀层变得致密均匀,电结晶生长形态呈现层状;镀层的致钝电流密度(i_(pp))和维钝电流密度(i_p)显著降低,极化电阻R_p增大,镀层具有良好的耐蚀性能。

The effect of La^（3＋） on the corrosion behavior of Zn-Fe alloy coating in acid solution were investigated.The corrosion behavior of Zn-Fe alloy coating was studied by the linear sweep voltammetry and AC impedance in 0.20 mol/L sulfuric acid solution at 30℃.The microstructure of Zn-Fe alloy coating before and after corrosion was studied by XRD and SEM.The results indicated that the grain size of Zn-Fe alloy coating turned smaller,the preferred orientation of Zn-Fe alloy coatings were not changed and the intension of diffraction for crystal planes were affected after adding lanthanum salt.When 0.90 g/L La_2（SO_4）_3 was added into the electrolytes,the coatings of Zn-Fe alloy were more uniform and close together,and the shape of electrocrystallization turned to layer.The i_（pp） and i_p of Zn-Fe alloy coating were reduced evidently,R_p was increased,and the Zn-Fe alloy coating had better corrosion resistance.