模拟混凝土孔隙液中钢筋表面膜组成与腐蚀行为的关联

CORRELATION BETWEEN COMPOSITION OF REINFORCING STEEL SURFACE FILM AND STEEL CORROSION BEHAVIOR IN SIMULATED CONCRETE PORE SOLUTIONS

采用XPS分析钢筋经模拟混凝土孔隙液浸泡后表面膜的化学组成,结合线性极化法和动电位扫描阳极极化曲线测试,研究钢筋在模拟混凝土孔隙液中表面膜化学组成与腐蚀电化学行为的关联.结果表明:钢筋在纯模拟液中处于钝化状态.在含Cl和不同pH值的模拟混凝土孔隙液中,随着Cl^-浓度的增加和pH值的降低,钢筋的腐蚀电位负移,电流密度增大;钢筋表面钝化膜Fe^(2+)的含量增加,Fe^(3+)的含量减少.当模拟液中外加Cl^-浓度达0.6mol/L或pH值降至11.31时,钢筋表面不发生钝化,但加入0.24mol/L NaNO_2缓蚀剂后又可使钢筋钝化从而抑制腐蚀.

It is well known that reinforcing steel in concrete can be protected from corrosion by forming a compact passive film on its surface in a concrete pore solution with high alkalinity. The corrosion behavior of the steel is related to its passivation and depassivation. The pH value and the C1- concentration in a concrete pore solution are of the most important parameters affecting the passivity of reinforcing steel in concrete. In the present work, XPS analysis, linear polarization and potentiodynamic anodic polarization tests were used to study the relationship between the electrochemical corrosion behavior of reinforcing steel immersed in a simulated concrete pore solution and the chemical composition of the steel surface film C1- concentration or the decrease of the pH value The results showed that with the increase of the in the solution, the corrosion potential of the steel shifted negatively and its corrosion current density rose, and the Fe^2＋ content of the steel surface film increased and the Fe^2＋ content decreased. The steel was in an active state in the solution with C1- concentration higher than 0.6 mol/L or pH lower than 11.31, and the addition of 0.24 mol/L NaNO2 to the solution could protect steel from corrosion.