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采用恒电位极化方法研究了X70钢在NaHCO_3溶液中的缝隙腐蚀行为,分析了Cl~-浓度和极化电位对X70钢缝隙腐蚀萌生及发展的影响,探讨了X70钢在NaHCO_3溶液中的缝隙腐蚀机理。结果表明:在-0.4V恒电位极化下,缝隙内X70钢在NaHCO_3溶液中可以发生局部腐蚀。缝口处首先发生酸化,并逐渐往缝底扩展。随着腐蚀的发展,酸化加剧,后期发生析氢反应,阴极反应由溶解氧的还原转变为H+的还原。加入Cl~-不改变缝内X70钢的腐蚀机理,但随着Cl~-浓度的增大,缝内腐蚀速率增加。随着极化电位的提高,缝隙内X70钢的腐蚀部位逐渐往缝底移动,同时发生点蚀。而缝隙腐蚀的萌生区域由极化电位及电位下降的程度决定。
The corrosion behavior of X70 steel in NaHCO 3 solution was studied by potentiostatic polarization method. The effects of Cl ~ - concentration and polarization potential on the initiation and development of crevice corrosion of X70 steel were analyzed, and the gap between X70 steel and NaHCO 3 solution Corrosion mechanism. The results show that local corrosion of X70 steel in NaHCO_3 solution can occur locally at -0.4V potentiostatic polarization. Suture at the first acidification occurs, and gradually extended to the bottom of the seam. With the development of corrosion, acidification aggravate, late hydrogen evolution reaction, the cathode reaction by the reduction of dissolved oxygen into H + reduction. The addition of Cl ~ - did not change the corrosion mechanism of X70 steel in the seam, but with the increase of Cl ~ -, the corrosion rate in the seam increased. With the increase of polarization potential, the corrosion site of X70 steel in the gap gradually moves towards the bottom of the seam, and pitting corrosion occurs at the same time. The crevice corrosion initiation area is determined by the degree of polarization potential and potential decline.