扫描微电极法研究钢筋局部腐蚀行为

Study on Localized Corrosion Behavior of Reinforcing Steel by Scanning Microelectrode Technique

关键词:  钢筋,局部腐蚀,扫描微电极,缓蚀剂

Key words:  reinforcing steel,localized corrosion,scanning microelectrode technique,inhibitor

摘要:

应用扫描微电极法原位测量了模拟混凝土孔隙液中钢筋表面微区的电位分布,并结合动电位极化曲线的测量,研究了钢筋的局部腐蚀行为及模拟混凝土孔隙液pH值和Cl-浓度对它的影响.结果表明,在饱和Ca(OH)2溶液中,钢筋处于钝态,其表面微区电位分布为动态平衡;溶液的pH值降低和外加一定浓度的Cl-后,钢筋表面微区电位分布随之变化.当表面微区电位分布出现固定的突出电位峰时,钢筋发生了点腐蚀.在pH=12.00,外加Cl-浓度为0.05 mol/L或pH值降至10.16的Ca(OH)2溶液中,钢筋表面去钝化,发生腐蚀.

Abstract:

In this work,the scanning microelectrode technique and potentiodynamic polarization were used to study the localized corrosion behavior of the reinforcing steel in simulated concrete pore solution with different pH values and chloride ion concentrations.It has been found that the reinforcing steel bar exhibits different corrosion characteristics in different conditions.There are some unstable micro-pitting nuclei on the surface of the steel in pure saturated Ca(OH)_2 solution and the steel remains passivated.However,the potential distribution on the steel surface changes with the addition of Cl~-or/and the reduction of pH value in the solution.The pitting corrosion of the steel occurs quickly when there are some obvious stable potential peaks on the steel surface and the height of one or some maximum potential peaks increases with time.Steel depassivation initiates and the corrosion takes place when additional Cl~-concentration reaches 0.05 mol/L in the Ca(OH)_2 solution with pH=12.00 or the pH of the solution falls to 10.16.