Rapid Quantitative Spectroelectrochemical Responses of Hydrogel-based Sensors for the in situ Evaluation of Corrosion Inhibitors on Steel

A direct sensor to quantitatively evaluate the inhibitory performance of a range of fatty acids (from formic to behenic) as corrosion inhibitors for steel is described. The sensor consists of a buffered polymeric hydrogel of 2-acrylamido-2-methylpropanesulfonic acid and poly(acrylic acid), equilibrated in potassium ferricyanide. This sensor responds to soluble transition metal ions by complexation to produce metal hexacyanoferrate, a process which rapidly induces measurable photonic and impedimetric changes within the hydrogel. X-ray photoelectron spectroscopy (XPS) was utilized to characterize differences in the surface chemistry across the range of inhibitors studied and to connect this work to other studies that investigated the surface coverage of some of the same molecules on steel. The contextualization of our simple, quantitative sensor responses via XPS and published literature suggest an improvement over current corrosion testing techniques, offering earlier, in situ detection with an understanding of the surface processes usually limited to advanced or high-vacuum techniques