Study on electrochemical characteristics of reinforced concrete corrosion under the action of carbonation and chloride

Considering parameters of corrosion area ratio and mass loss degree, the half-cell potential method and linear polarization method were applied to study the corrosion state of steel bars under the influence of carbonation, chloride salt and compound environmental action. X-ray photoelectron spectroscopy (XPS) was used to measure steel corrosion under coupling action and the effect of sodium nitrite rust inhibitor in the compound environment was studied. The results show that the corrosion rate of steel under carbonation, chloride salt and compound environment increases in the beginning and then decreases. In the chloride environment, sufficient moisture inside the concrete at the initial stage of curing induces a faster corroding. With the destruction of the passive film on the surface of the steel bars together with the balance of internal and external humidity, the corrosion rate tends to stabilize. At the following curing stage, the corrosion rate decreases as the degree of steel corrosion increases and the corrosion layer is formed. Carbonation reduces the alkalinity around the passive film and damages the passive film, which accelerates the corrosion happening. The following development of the corrosion layer of steel bars limits the corrosion rate. The corrosion degree in the compound environment is more serious than that under the condition of single factor action. Under electrochemical action, the order of product components resulting from steel corrosion are Fe2O3, Fe3+-Ca2SiO4 and FeO from high to low. Nitrite oxidizes the unstable Fe2+ into stable Fe3+ and precipitates on the surface of the steel to form a passivation film, which has a good anti-rust effect.