The impact of sandblasting as a surface modification method on the corrosion behavior of steels in simulated concrete pore solution

This investigation aimed to study the passivation and corrosion performance of sandblasted steel in a concrete environment. The surfaces of the steel specimens were modified using sandblasting method for three durations: 5, 10, and 15 min. The specimens were immersed in the chloride-free concrete pore solution for 14 days and then 3% by weight of chloride ions were added to the solution. The specimens were then kept in the chloride-contaminated pore solution for 60 days. Results from the electrochemical tests indicated that the passive layer formed on the surface on all specimens exposed to a simulated concrete pore solution were highly disordered n-type semi-conductors. In all specimens, except the 15 min sandblasted ones, the presence of chloride ions decreased the slope of the Mott-Schottky plots and increased the donor density which indicated formation of a thinner passive layer and corrosion. The results of electrochemical experiments on steel rebar exposed to chloride-contaminated pore solution showed significant improvement in corrosion resistance of the sandblasted specimens. This improvement was proportional to the increase in the sandblasting time. Microscopic analysis of the steel specimens at the end of the experiment showed the formation of a dense calcium-rich crystalline structure on the surface of sandblasted specimens. The density and the uniformity of the calcium-rich layer increased by increasing the sandblasting time. It was hypothesized that the formation of this layer combined with the enhanced passive layer in sandblasted specimens were the reasons for the improvement in corrosion resistance of the sandblasted steel specimens.