基于多物理场耦合的大气环境下碳钢点蚀演化及速率预测模型

Evolution and Rate Prediction Model of Pitting of Carbon Steel in Atmospheric Environment Based on Multiphysical Fields

为揭示大气环境下碳钢点蚀演化规律,基于电化学腐蚀机理,耦合三次电流分布、物质传递和变形几何多物理场建立碳钢点蚀演化的数值模型。基于此,分析pH值、NaCl浓度和相对湿度(Relative humidity,RH)对点蚀速率的影响并建立点蚀速率预测模型。研究表明:点蚀形态由初始圆锥形向半球形转变,最后发展成圆柱状;pH值处于6.0~7.0范围内,碳钢点蚀速率出现明显下降,最大降幅为23.96%;NaCl浓度在0.5%~1%(质量分数)时,增加NaCl浓度对点蚀速率提升明显,最大增幅为10%;碳钢点蚀速率在RH为72%~77%内存在极值;点蚀速率预测值与试验值误差在5%以内。以上表明本工作建立的数值模型和预测公式可用于碳钢点蚀演化和速率预测。

To reveal the evolution law of the pitting of carbon steel in the atmospheric environment,a numerical model of pitting was established on the basis of the electrochemical corrosion mechanism.Meanwhile,it is also coupled with tertiary current distribution,material transfer and deformation geometry multiphysics fields.Based on the validated numerical model,an analysis was conducted by the effects of pH,NaCl concentration and relative humidity(RH)on the pitting rate.Furthermore,the prediction model of pitting rate was established.The results show that the pitting shape changes from conical to hemispherical and ultimately develops into a cylindrical shape.When the pH value is in the range of 6.0 to 7.0,the pitting rate remarkably decreases,with the maximum reduction being 23.96%.When the NaCl concentration falls within the range of 0.5%to 1%(mass fraction),an increase in NaCl concentration significantly impacts the pitting rate,with a maximum increment of 10%.When the RH ranges from 72%to 77%,the pitting rate of carbon steel exhibits an exceptionally high level.The error between the predicted pitting rate and the test is less than 5%.These indicate that the numerical model and prediction formula established in this work are applicable to predicting the pitting evolution process and pitting rate of carbon steel.