Optimized Cr Concentration in Reinforcement Steel for High Corrosion Resistance in Simulated Pore Solution by Electrochemical and Cyclic Corrosion Tests

摘要

Nine samples of low-carbon steel were prepared by varying composition of Cr and Mn. The weight% of Cr and Mn in samples are 0.2Cr, 0.5Cr and 5Cr, and 0.5Mn, 1.0Mn and 1.5Mn respectively.The electrochemical tests such as corrosion potential, EIS, Linear polarization and Cyclic polarization were conducted on samples in simulated pore solution with and without the presence of 3.5% NaCl. Separately, samples were exposed to wet-dry corrosion test and their corrosion products were examined by XRD and FTIR. Further, oxidised surface was studied by SEM/EDS.The samples show passive behaviour in chloride free pore solution but passivity breaks after chloride addition. Even, 5Cr containing steels could not hold passive characteristic in chloride medium. In wet-dry corrosion test, 5Cr containing steels develop loose and voluminous corrosion products which is highly detrimental for rebar application.On the contrary, the lower Cr containing steels, 0.2Cr and 0.5Cr, produce thin and adherent rust in wet-dry corrosion test. In electrochemical test, these steel samples too transfer from passive to active state after chloride ion addition in pore solution but their behaviour is superior. More particularly, two steel chemistry 0.2Cr, 0.5Mn and 0.5Cr, 1.5Mn show a sign of repassivation and pitting resistance respectively.