New Rapid Nondestructive Testing Method for Detecting and Quantifying Steel Corrosion in Saltwater and Clay Soil Using the Vipulanandan Impedance Corrosion Model

In this study, carbon steel corrosion was evaluated in salt water solutions and moist bentonite clay using the newly developed non-destructive electrical method, which can be easily adopted in the field for real-time monitoring, and the results were compared to some standard test methods such as weight loss. The average weight loss in 10% salt solution in one year was 1.05% and corrosion rate was 1.54 mm/year. The use of the new nondestructive electrical method was to detect and quantify the surface and bulk corrosion. Tests were performed to first verify the best electrical property that will be highly sensitive and represent the steel corrosion. The findings from this study indicated changes in the newly developed electrical corrosion index for the surface (2D representation) and the resistivity (second order tensor, 3D representation) for the bulk material using the Vipulanandan Corrosion Impedance model. Corrosion development in 750 mm long steel specimens was studied in the 3.5% salt solution (simulating sea water) for 500 days. The surface corrosion was quantified using the new electrical corrosion index parameter, and the change was over 200%. The steel in the moist bentonite clay showed a surface corrosion of 37.5%. The change in the bulk resistivity along the length of the steel specimen was over 44,300 times (4,430,000%) in 3.5% salt solution compared to about 1.05% change in the weight in one year. Hence the electrical resistivity for the bulk material and the corrosion index for the surface corrosion are highly sensing parameters for detecting and quantify the corrosion in the steel.