通过室内埋片实验研究了X70钢在内蒙古西部地区苏里格大气田土壤中的腐蚀行为.在不同含水量的土壤中进行埋片,然后测定试样的自腐蚀电位和腐蚀速率随时间的变化关系,最后进行了试样的形貌观察和腐蚀产物的EDS和XRD的分析.实验结果表明,随着时间的延长,其腐蚀速率是不断变化的.在不同含水量的土壤中钢试样经过相同时间的腐蚀后,在水的质量分数为10%土壤中的腐蚀最严重,5%次之,20%腐蚀最轻微.经过30 d的腐蚀后,试样的腐蚀产物主要为铁的氧化物(Fe2O3,Fe3O4).对试样的自腐蚀电位Ecorr监测结果表明,30 d内不同含水量土壤中钢的自腐蚀电位变化规律是不同的,其中水的质量分数为20%的土壤中的Ecorr最低,5%的土壤中的Ecorr最高.Corrosion of X70steel in the soil of Sulige Gas
With epoxy coal tar as the coating material, the electrochemical corrosion behavior of Q235 with different kinds of bulk coating holidays has been investigated with EIS (Electrochemical Impedance Spectroscopy) in a 3.5vol％ NaCl aqueous solution. The area ratio of bulk coating holiday to total coating area of steel is 4.91％. The experimental results showed that at free corrosion potential, the corrosion of carbon steel with disbonded coating holiday is heavier than that with broken holiday and disbonded & broken holiday with time; Moreover, the effectiveness of Cathodic Protection (CP) of carbon steel with broken holiday is better than that with disbonded holiday and disbonded & broken holiday on CP potential-850 mV (vs CSE). Further analysis indicated that the two main reasons for corrosion are electrolyte solution slowly penetrating the coating, and crevice corrosion at steel/coating interface near holidays. The ratio of impedance amplitude (Z) of different frequency to minimum frequency is defined as K value. The change rate of K with frequency is related to the type of coating holiday.
