Study On Corrosion Behavior Of Steel Rebar Of Reinforce Concrete Under Acid-rain Environment

Concrete structure is one of the most widely applied structures in the world. But reinforced concrete is easy to be corroded in some severe atmosphere, especially under the effect of acid rain. Corrosion of steel rebar in the reinforcement concrete will significantly shorten the service life of the structure, and reduce its safety.Rain of Chongqing is simulated as corrision situlation in the article, the corrosion of two common rebar steels, namely No. 45 and Q235 steel, was studied through electrochemical methods, such as polar curve and impedance, under the environment of simulated acid rain and reinforcement concrete pore solution. The corrosion of reinforced concrete under the indoor periodical immersion in simulated acid rain and atmosphere outside was investigated by measure the change of pH value of the immersion solution, weight of the samples and the electrochemical impedance of the rebar. It was roughly discussed that the dynamic characteristics of corrosion and the structure of electrode interface occurred in the interface of the rebar.The results showed that with the immersion time increase of reinforce concrete in acid rain solution, the pH value of solution increased gradually, but the change range was decreased. Corrosion rate of reinforce concrete periodically immersed in acid rain solution indoors was far beyond that in atmosphere outside.With the decrease of the pH value and the increase of the concentration of SO₄^2-, Cl^- and NO₃^- in simulated acid rain, the corrosion rate of steel rebar is rising. The corrosion of steel rebar was obviously accelerated by the depolarization of Cl^-, while the effect of SO₄^2- and NO₃^- was very small on the corrosion. As the immersion time goes on, the corrosion rate increased firstly, then decreased, and increased again later, which indicated that the corrosion product layer on the steel rebar changed and had some effect on the corrosion rate of rebar during the its immersion.Rebar was blunt usually in simulated pore solutions of reinforcement concrete. But the corrosion rate of rebar was raised with the addition of corrosive acid rain, especially with the increase of the concentration of Cl^- ion. However, with the increase of SO₄^2- and NO₃^-, corrosion rate of steel 45 was decreased, and that of Q235 was increase to some extent. As the immersion time goes on, pitting corrosion of rebar could occur.In the simulated acid rain and pore solution of reinforcement concrete, the corrosion resistance of 45 steel is better than that of Q235 steel, the reason might be that there are some alloy elements in steel 45 could result deactivation.