Real-Time Monitoring of Short-Term Steel Corrosion in Cement and Soil

The corrosion process is defined as an electrochemical reaction that causes the deterioration and loss of material which adversely affects the critical properties of a material such as its microstructure, mechanical properties, and physical appearance. Corrosion of steel is of particular interest as steel is the largest volume of metal used in the construction of most structures including buildings, bridges, storage facilities, and pipelines. Several testing methods have been used to detect and quantify corrosion such as visual inspection, weight-loss method, radiography, acoustic monitoring. However, most of these methods have limitations including field applications. In this study, the Vipulanandan Impedance Corrosion Model was used to assess and quantify the corrosion occurring in steel subjected to different environmental conditions. For this study, three different specimens were considered: (1) cement-steel casing immersed in 3.5 % saltwater for an observation period of 250 days, (2) steel bar in 10% moist sand for an observation period of 70 days, and (3) steel bar in 40% moist clay for an observation period of 70 days. The above steel specimens were allowed to corrode for the set observation period and the impedance data was collected from each specimen which was then used to get the model parameters: bulk resistance (Rb), contact resistance (Rc) & interface resistance (Ri), and contact capacitance (Cc) & interface capacitance (Ci) for the Vipulanandan Impedance Corrosion Model. The electrical corrosion index for each specimen was then observed over time to understand the corrosion mechanism.