Effect of Na2SiO3 content on passivation and corrosion behaviour of steel in a simulated pore solution of Na2SiO3-activated slag

This paper aimed to investigate the effect of the Na2SiO3 content on steel corrosion behaviour in simulated Na2SiO3-activated slag (NSAS) pore solutions. The simulated NSAS pore solutions were prepared from a Na2SiO3-activated slag extraction solution. Aggressive chloride ions were gradually added to the simulated NSAS pore solutions, and the passivation and corrosion properties of steel in the solutions were studied. The chloride threshold value was also investigated. The results indicated that the content of Na2SiO3-activator greatly influenced the resistance of the steel to chloride-induced corrosion. When the Na2SiO3-activator content is less than or equal to 6% (Na2O% by slag mass), the corrosion resistance of steel in simulated NSAS pore solutions is enhanced as the Na2SiO3-activator content increases. However, further increases in the Na2SiO3-activator content beyond 6% result in a reduction in corrosion resistance. When the alkalinity of the simulated NSAS pore solution is markedly high (above pH 13), the passive film becomes unstable due to the generation of soluble ferrate (FeO42−).