用丝束电极研究模拟碳化混凝土孔隙液中缓蚀剂对碳钢局部腐蚀的抑制行为

摘要

应用丝束电极(WBE)的电位/电流扫描技术,研究了含Cl-的模拟碳化混凝土孔隙液中,Q345B碳钢局部腐蚀在空间和时间上的发生和发展特征,同时比较了四乙烯五胺(TEPA)和亚硝酸钠缓蚀剂对局部腐蚀抑制能力的差异.结果表明NO-2离子能快速渗透腐蚀产物层,并抑制锈层下的碳钢活性溶解,而乙烯胺由于在锈蚀层内的扩散速率低,初期反而会促进锈层下的局部腐蚀,随着烯胺分子扩散并吸附于锈蚀层/金属界面处,碳钢活性溶解才受到抑制.电化学阻抗谱(EIS)可反映局部腐蚀的萌发,但难以表征缓蚀剂在碳钢表面的不均匀吸附特征.基于丝束电极表面电位/电流分布所提出的局部腐蚀因子(LF),可定量表征腐蚀的不均匀特征以及缓蚀剂对局部腐蚀的修复能力.%The initiation, growth, and temporal and spatial distribution of localized corrosion of Q345B carbon steel in carbonated concrete pore solutions (pH 9.6) containing 0.1 mol·L-1 Cl- ions were investigated using a potential and galvanic mapping technique based on a wire beam electrode (WBE).Different mechanisms for repair and suppression on the stable localized corrosion by tetraethylenepentamine (TEPA) and nitrite were compared.The results indicate that nitrite can inhibit the active dissolution of steel beneath the rust layer because of the fast penetration of nitrite into the rust layer.However, TEPA can promote active dissolution under the rust layer initially because of its slow penetration rate through the rust layer.The localized active dissolution was only refrained after a long time because of TEPA molecules permeating into the interface between the rust layer and the steel matrix.Electrochemical impedance spectroscopy (EIS) was useful in allowing us to determine how the localized corrosion was initiated but failed to indicate the heterogeneous adsorption of the inhibitors on steel.A new localized corrosion factor (LF) based on galvanic mapping is proposed and is shown to be effective for the characterization of the localization of corrosion and the inhibition effect of inhibitors on localized corrosion.