Electrophoretic Interface Expansion: A Spectro-Electrochemical Approach Inspired by Gel Electrophoresis to Determine Degradation Mechanisms in Copper and Nickel

Spectroelectrochemical signature associated with the corrosion of copper and nickel metal strips have been investigated using chronoamperometry, UV-Visible spectroscopy and electrochemical impedance spectroscopy (EIS) techniques. Inspired by gel electrophoresis, an in-situ method (named EPIX) was developed using 2 wt% gel prepared in 3.58 wt% NaCl to follow the movement of metal ions resulting from the corrosion of copper and nickel metal strips under an applied oxidative current bias and detected in the UV-Visible spectrophotometer beam. The progression of the corrosion processes for both nickel and copper were further analyzed by applying different voltages and by using gel matrices of different pHs and salt concentrations. From the chronoamperometric responses, it was observed that for all the cases current density decreased with time initially and eventually plateaued except for the case of acidic gel solution where current density was found to increase initially before becoming plateaued during corrosion of copper metal strip whereas for the corrosion of nickel metal strip, current density was found to increase initially with time and eventually plateauing to a constant current density value for all the cases. All the characteristic absorption bands associated with octahedral copper(II) and nickel(II) ions were observed during the corrosion of the metal strips in the gel medium. The decay rate of the metal strips during the corrosion event was calculated and found to increase with decreasing potential, increasing applied potential, and higher salt concentration in the reaction medium.