Effect Of Inorganic Salts Solution On Steel Corrosion

Steel corrosion is one of the main failure modes of reinforced concrete structure. Study on the regulation of steel corrosion can help to find effective protection measures to reduce the rate of corrosion reaction, and delay the time of corrosion failure. Thus it can help to extend the service life of reinforced concrete structures.In this study, different kinds and different concentration of salt solutions were used to simulate the concrete environment. On the one hand, the change of the solution color and the size of the pitting area on the steel surface after a certain period of time were observed to get the corrosion regulation on the macro level, on the other hand, the change of steel’s potential value with time measured by electrochemical work station, the change of composition and concentration of salt solution, and the change of p H value were observed to more intensively study the corrosion mechanism and corrosion regulation in different salt solutions.Similar study was carried out to observe the difference of corrosion rate compared with that of the steel in salt solution by imbedding the steel into concrete specimens which were prepared with the combination of normal concrete raw materials and salt solution with different kind and different concentration. This result provides additional reference for the protection of steel corrosion of reinforced concrete structures in practical application.It is found that when the steel is immersed in the salt solution with single corrosion ion, the corrosion ion’s corrosion ability to the steel’s end face is positively related with its concentration, and the steel’s potential value continuously decreased with time until down to stable.The corrosion anions used in this study were SO42- and C l-, it is shown that their corrosion ability under the same concentration is SO42->Cl-; as for the cation, Na+ and NH4+, the corrosion ability is Na+<NH4+. When conbined the two corrosion ions with the same concentration,the mixed ions’ corrosion ability is between the two single corrosion ions at the same concentration. The conclusion is furtherly verified by the experimental results of the steel in concrete specimens.The corrosion rate of the steel in salt solution with single corrosion ion is increased with temperature, thus less time of the corrosion potential is needed to reach the stable value, and the corrosion ability of corrosion ions is slightly increased.Four common kinds of rust inhibitors were choosed to put into the salt solution in which a certain degree of corrosion reaction had been finished, it is found that all the steel’s corrosion potential recovered at different degree, and according to the recovery rate of the corrosion potential at the same putting time, the corrosion ability of the four kinds of rust inhibitors to steel from weak to strong is: Cr O42-<HPO42-<NO2-<Mo O42-. If conbined two rust inhibitors with the same concentration, the rust inhibition ability of the mixed rust inhibitors is better than a single rust inhibitor at the same concentration.By continuously measuring the corrosion potential of the steel in concrete specimens and comparing with that of the steel in salt solution, it is found that corrosion potential of the steel in concrete specimens maintains a higher value for a very long time, and the corrosion rate is slower than that of the steel in salt solution, thus causes the potential value not reach the stable value even at the end of the test. However, the corrosion trend of the steel in concrete specimens which mixed by salt solution of different kind and concentration is similar as that of the steel in salt solution. This indicates that the corrosion ions to steel both in salt solution and concrete specimens have the same corrosion regulation, but the corrosion rate of the steel in concrete specimens is obviously slower than that of the steel in salt solution.