Initial Corrosion of Steel in Cement-Based Composites in Saline Soil at 65°C

In practice, the initial corrosion of steel is particularly important in terms of the assessment of serviceability and durability. Corrosion initiation of steel is strongly affected by ion chemical compositions and concentration, which are essentially different in saline soils than in marine, coastal, airborne, and deicing salt environments. However, of even greater importance is the effect of temperature. This study characterized the time required for corrosion initiation of steel in cement-based composites exposed to a simulated saline soil solution at 65 degrees C. Steel electrode samples were used to evaluate the time to initial corrosion in the simulated solution of saline soil at 65 degrees C (and at 45 degrees C and 25 degrees C for comparison) via electrochemical impedance spectroscopy. Cement-based composite cube samples were made to measure the chloride diffusion behaviors. The higher temperature led to a decrease in free chloride, which is essential to the initial corrosion of steel, but an increase in chloride diffusion depth and chloride concentration. Using these data, Fick's second law was employed to derive the prediction equation for time to corrosion initiation. The results in this paper are expected to expand and improve the body of knowledge related to the initial corrosion of steel, which will facilitate prediction of the service life of cement-based composites structures in a saline soil environment at 65 degrees C.