钨酸盐对碳钢缓蚀机理的研究

Study of Corrosion Inhibition Mechanism of Carbon Steel with Tungstate

运用旋转圆盘电极测定了碳钢在钨酸钠溶液中的阳极极化曲线 ,研究了电位扫描速度、钨酸钠浓度、氯离子、钙离子及镁离子对极化曲线的影响。实验发现 :在电极转速为 10 0 0r·min-1、电位扫描速度为 5mV·s-1时 ,体系仍处于稳态 ;在去离子水中 ,钨酸钠浓度为 1× 10 -4 mol·L-1时可使碳钢钝化 ,在 ρ(Cl-) =5 0mg·L-1的水溶液中 ,钨酸钠浓度达 1× 10 -2 mol·L-1时碳钢才能钝化 ;氯离子质量浓度的增加使碳钢表面钝化膜的致密程度下降 ,容易发生点蚀 ;水中钙离子的存在不利于碳钢表面形成钝化膜 ,浓度为 1× 10 -3 mol·L-1的镁离子对碳钢的阳极极化曲线有显著影响。碳钢表面的ESCA分析结果发现膜中有镁元素的存在 ,说明介质中的镁离子参与了表面的成膜过程。

The anodic polarization curves of carbon steel in solutions containing tungstate were measured using rotating disc electrode (RDE).The effects of scan speed of potential and concentration of tungstate,chloride ions,calcium ions and magnesium ions on polarization curves were studied.The results showed that the system was still in stable state when the rotating speed of RDE was 1000 r·min -1 even though the potential scanned at such a quick speed as 5 mV·s -1 .In deionized water,carbon steel could be passivated with 1×10 -4 mol·L -1 tungstate,but it should be passivated with 1×10 -2 mol·L -1 tungstate in 50 mg·L -1 Cl - solution.There was competitive adsorption between WO 4 2- and Cl -.Increase of Cl - in solution would reduce the quality of passivation film,so that pit corrosion took place on the surface of carbon steel more easily.Existence of Ca 2+ in solution was unfavorable to the formation of passivation film.1×10 -3 mol·L -1 Mg 2+ in solution could affect the polarization curve markedly.It could be found from results of ESCA that Mg existed in the passivation film of carbon steel.This indicated that Mg 2+ ions in solution were involved in the formation of the passivation film.