دانلود رایگان مقاله آزمون رشته های دریایی کم آلیاژ میلگردهای فولادی مقاوم در برابر خوردگی

abstract

Macrocell corrosion test and accelerated alternating wet–dry experiment combined with marine field test were employed to study the corrosion behavior of HRB400 carbon steel, 1.5Cr steel, and 5Cr steel in a simulated concrete pore solution and mortar. The macrocell current significantly decreases in samples added with Cr compared with that in HRB400 steel. The corrosion rate is decreased by Cr but increased by Cl−; as a consequence, the corrosion rates of 1.5Cr and 5Cr steel are lower than that of HRB400 steel. However, the corrosion products differ slightly in terms of the contents of α-FeOOH (goethite), γ-FeOOH (lepidocrocite), γ-Fe2O3, and Fe3O4 (maghemite or magnetite). The addition of Cr increases the content of the protective α-FeOOH and reduces the content of γ-FeOOH. Both ordinary and high-performance epoxy coatings remain intact after 1 year of marine field test. Among the bare steel rebars, HRB400 steel shows extensive localized corrosion on the surface, whereas 1.5Cr steel exhibits less severe corrosion. The scarcely visible corroded areas in 5Cr steel indicate that this rebar is in the passive state, consistent with results of the indoor accelerated test. Hence, the durability of concrete structures can be prolonged with the utilization of corrosion-resistant low-alloy rebars.

4. Conclusion

Through indoor accelerated corrosion test and marine field studies of HRB400 steel, 1.5Cr steel, and 5Cr steel, the conclusions we draw are summarized as follows: (1) HRB400 steel exhibits poor corrosion resistance; as the Cr content is increased, the corrosion rate is reduced; corrosion rate of 5Cr steel is the lowest and merely half that of the corrosion rate of HRB400. (2) The primary corrosion products of steels are a-FeOOH, g-FeOOH, and g-Fe2O3/Fe3O4; in 1.5Cr steel and 5Cr steel, protective a-FeOOH is the most dominant among the corrosion products, indicating that Cr promotes the formation of protective corrosion products. (3) After a 1-year field study in the splash zone in Zhanjiang, ordinary epoxy coatings and high-performance epoxy coatings are still intact without any obvious corroded zones; among the bare rebars, HRB400 and 1.5Cr steel present localized corrosion, whereas 5Cr steel does not have any corroded zone on its surface. Results of field study coincide with the predicted results, which prove that the utilization of corrosion resistant rebars can improve the durability of concrete structures.