局部腐蚀闭塞区内临界pH值的影响因素探讨

Factors Influencing Critical pH Value in Occlusion Area of Local Corrosion Area of Crude Oil Tank

原油储罐局部腐蚀闭塞区临界pH值的大小因闭塞体系和试验条件的不同而异,目前未研究其影响因素。通过模拟闭塞电池的方法,研究了金属储罐底局部腐蚀闭塞区内的临界pH值及其影响因素,并结合金属E-pH图指导局部腐蚀的电化学保护方法设计。结果表明:闭塞区存在临界pH值,其大小受极化电流密度和极化温度的影响不大,但极化电流密度和温度的增加会缩短溶液到达临界pH值的时间;闭塞区相对容积对临界pH值的影响较大,只有储罐底有孔和裂纹缝时才会发生闭塞反应;临界pH值在金属储罐罐底电化学保护中有指导意义。

Simulated occluded cell method was adopted to investigate the critical pH value at the local corrosion occlusion area of metal tank bottom and the factors influencing the pH value.The design of the electrochemical protective methods applicable to the tank was investigated in relation to E- pH diagram.Results showed that there existed a critical pH value in the occlusion area,and its value was slightly influenced by the polarization current density and temperature,while increasing polarization current density and temperature shortened the time for the pH value of the solution to reach the critical value.Moreover,the relative volume of the occlusion area had significant influence on the critical pH value,and no occlusion reaction occurred unless pores and cracks were present at the tank bottom.In general,the critical pH value was of some significance in terms of the design of the electrochemical protective methods for the crude oil tank made of metal.