Three-dimensional characterization of steel corrosion embedded in cement paste

Abstract

Abstract In this research, a micro X-ray computed tomography (μCT) technique was used to investigate the distribution of steel corrosion embedded in cement paste non-destructively. An electrochemical method was used to accelerate the corrosion of steels for two designed levels of corrosion (2% and 18%). For μCT observations, two camera lenses (0.4× and 4× camera lenses) were used to globally and locally investigate the tomography of un-corroded steels, corrosion products as well as cracks. The factors affecting the corrosion distribution, such as the immersion depth in NaCl electrolyte as well as the arrangement of cathode position were also investigated. Test results showed that corrosion started at a certain direction by forming pits. For both corrosion levels, the distribution of corrosion products is not significantly related to the position of cathode electrode but related to the distribution of cracks. More corrosion products accumulated at the steel surface where penetrating cracks occurred; whereas in the occluded cracks, the corrosion product was insignificant. Furthermore, the actual corrosion level was found to be related to the immersion depth in NaCl electrolyte. i.e., with the increase in the depth of immersion, the steel corrosion level increased.