42CrMo钢在氯离子溶液中的腐蚀行为研究

目的通过研究42CrMo钻具用钢在常温下不同Cl~-浓度溶液中的腐蚀行为,为其腐蚀速率的预测奠定一定基础。方法采用浸泡实验、电化学测试技术研究42CrMo在不同浓度NaCl溶液中的平均腐蚀速率和电化学特性,并结合SEM扫描电镜对浸泡58 h后的挂片试样进行分析。结果浸泡实验分析表明,当Cl~-达到60 g/L时,42CrMo钢的腐蚀速率达到最大值,为0.124 g/(m~2·h);当Cl~-浓度继续增大时,腐蚀速率随Cl~-浓度的增加而逐渐减小。开路电位Eocp分析表明,随着Cl~-浓度的增加,Eocp总体呈现下降趋势,显示出较大的腐蚀倾向性。极化曲线分析表明,阴极极化曲线的斜率明显比阳极大,并且自腐蚀电流密度在60 g/L Cl~-溶液中达到最大值,为5.952 35μA/cm~2。腐蚀形貌研究表明,42CrMo浸泡58 h后,表面的腐蚀产物分布并不均匀,均发生了局部点蚀现象。结论随着Cl~-浓度的不断增大,42CrMo钢的平均腐蚀速率呈现先增大后减小的趋势,且在Cl~-为60 g/L时,平均腐蚀速率最大。42CrMo钢在静态常温下高Cl~-浓度溶液中以局部点蚀为主,其电化学腐蚀过程主要受阴极去氧极化的控制。

Corrosion Behavior of 42CrMo Steel in Chloride Solution

The work aims to lay a foundation for predicting corrosion rate of steel for 42CrMo drilling tool use by studying its corrosion behavior provided with different Cl-concentration at normal temperature.Average corrosion rate and electrochemical characteristics of 42CrMo in NaCl solution of different concentrations (mass concentration,applicable to the full text) were studied by immersion experiment and electrochemical testing technology,and lacing film specimen was analyzed with scanning electron microscope after 58 h immersion.Immersion experiment analysis showed that corrosion rate of 42CrMosteel reached a maximum of 0.124 g/(m2 · h)when the Cl-concentration reached 60 g/L,the corrosion rate decreased gradually as the Cl-concentration increased when the Cl-concentration increased gradually (more than 60 g/L).Open circuit potential Eocp analysis showed that Eocp tended to decline as a whole with the increase of Cl-concentration,and showed clear tendency toward corrosion.Polarization curve analysis showed that slope of cathodic polarization curve was significantly higher than that of anode,and the corrosion current density reached the maximum 5.952 35 μA/cm2,in 60 g/L NaCl solution.Corrosion morphology study of 42CrMo showed that the surface corrosion products were unevenly distributed and subject to local pitting after 58 h immersion.Average corrosion rate of 42CrMo steel first increases and then decreases as Cl-concentration increases continuously,and it reaches the maximum when the Cl-concentration is 60 g/L.42CrMo steel in static state at room temperature is mainly subject to local pitting in high content of Cl-solution,and the electrochemical corrosion process is mainly controlled by cathodic oxygen depolarization.