Nitrite inhibitor is a kind of most effective inhibitory corrosion additive used in reinforced concrete. This paper expounded the inhibiting mechanism and physical property of nitrite in concrete. Moreover, the recent progress and application condition at home and abroad were summarized. Meanwhile, corresponding methods for detecting nitrite ion concentration is proposed. Additionally, the inhibition practice on corrosion protection of reinforcing bar in concrete was presented. The long-term inhibiting effectiveness of nitrite ion in concrete when the n(NO2-)/n(Cl^-) ratios were above the threshold values in concrete was obtained. Finally it is confirmed that critical molar ratio of n(NO2-)/n(Cl^-) increased with differential nitrite ion concentration, higher cathode, and anode area ratio in steel bar.

The microstructures of steel bars were studied by X-ray photoelectron spectroscopy (XPS), and the mechanism of corrosion of steel bars under the corrosion factors was elucidated. The results show that the passivation film and corrosive surface of the steel surface in the solution of the chloride-containing salt were coarser and the surface state was denser. The main corrosion products are FeOOH and FeO. The surface of the steel immersed in the simulated carbonized solution had loose pores. The main components are FeOOH, Fe₃O₄, and Fe₂O₃. The surface of the steel bar has a large amount of yellowish brown corrosion products in the simulated carbonization and chloride salt. The surface of the corrosion products was stripped and the main components are FeOOH, Fe₃O₄, and FeCl₃, where the content of FeOOH is as high as 60%. The peak value of iron is gradually increased from the simulated chloride salt solution to the carbonized solution to the combined effect of carbonation and chloride salt; the iron oxide content is increased and corrosion of steel is obviously serious.

The influence of chloride ions content on the sea sand concrete performance was investigated through testing the sea sand mortar strength in this paper. The concrete strength rule was analyzed to discover the early strength for the sea sand concrete by the presence of chloride. In addition, the XRD microscopic analysis and TG/DTA were observed the composition of concrete to research the influence on hydration processes of concrete caused by sea sand, and from two aspects to find out the differences of the internal microcosmic structure and the chemical composition respectively. And Micro-technique was used to determine the water-soluble chloride ion concentration of different types of sea sand concrete which were maintained 28 days. The results show that the chloride ion can improve concrete strength value and the concentration of free chloride increases with the rise of extraction temperature.