温度对P110钢在水泥挤出液中钝化膜性能的影响

Effect of Temperature on the Performance of P110 Steel Passivation Film in Cement Extract Solution

目的探究P110套管钢在不同温度下生成的钝化膜的性能差异,找到能使P110套管钢生成最稳定钝化膜的温度,同时了解该温度下氯离子对钝化膜的破坏规律。方法利用极化曲线、交流阻抗谱(EIS)和Mott-Schottky测试,研究了P110套管钢材料在pH值为13.0的水泥挤出液中浸泡4 d的钝化行为,讨论了在低、中、高(40、65、90℃)三种温度下生成的钝化膜的稳定性,并用扫描电子显微镜(SEM)对各试样表面微观形貌进行观察。最后在溶液中加入不同浓度的氯离子,通过测试极化曲线了解氯离子对钝化膜的破坏规律。结果试样在40、65、90℃下的腐蚀电流密度分别为2.2727×10-6、4.0452×10-7、1.7081×10-5 A/cm2,膜电阻分别为100 100、238 200、5480?·cm2。40、65℃下所生成的钝化膜呈p型半导体特征,而90℃下呈双极型半导体特征。65℃下,随着氯离子浓度的增加,试样的腐蚀电位负移,耐蚀性逐渐降低,腐蚀速率增大,当浓度达到0.1mol/L时,钝化膜的膜层结构已被破坏。结论 P110套管钢在pH值为13.0的水泥挤出液中浸泡4d,表面能够生成钝化膜。在65℃溶液中生成的钝化膜耐蚀性最好,膜层结构更加致密,40℃次之,90℃最差。氯离子对钝化膜有侵蚀作用,高浓度的氯离子可以直接导致稳定钝化膜的破坏。

The work aims to explore the difference of performance of P110 casing steel passivation film formed at different temperature and find out the temperature that can make P110 casing steel form the most stable passivation film and to know the failure law of the passivation film caused by chloride ions at this temperature.The passivation behavior of P110 casing steel immersed for 4 days in cement extract solution with pH value of 13.0 was studied by polarization curves method,electrochemical impedance spectroscopic(EIS)and Mott-Schottky test.The stability of passivation film formed at low,middle and high temperature(40℃,65℃and 90℃)was discussed and the surface morphology of each sample was observed by scanning electron microscopy(SEM).Finally,different concentrations of chloride ions were added into the cement extract solution,and the polarization curve method was used to investigate the failure rules of chloride ion to the passivation film.The corrosion current densities of the specimens at 40℃,65℃and 90℃were respectively as follows:2.2727×10^-6 A/cm^2,4.0452×10^-7 A/cm^2 and 1.7081×10^-5 A/cm^2;and the membrane resistance were respectively as follows:100 100Ω·cm^2,238 200Ω·cm^2 and 5480Ω·cm^2.The passivation films formed at 40℃and 65℃showed p-type semiconductor feature and the passivation films formed at 90℃showed a bipolar semiconductor feature.With the increase of chloride ion concentration,the corrosion potential of the sample negatively shifted,the corrosion resistance gradually decreased and the corrosion rate increased.When the concentration reached 0.1 mol/L,the film structure of the passivation film was destroyed.The surface of P110 casing steel can form a passivation film after being immersed in the cement extract solution with pH value of 13.0 for 4 days.The corrosion resistance of the passivation film formed in the solution at 65℃is the best and the film structure is more compact which is followed by that at 40℃.The films formed at 90℃are the worst.The chloride ion can erode the passivation film and the high concentration of chlorine ion can directly cause the destruction of the stable passivation film.