Kinetic Study of Rare Earth (III) Corrosion Inhibitors on Cold Rolled Steel Using Electrochemical Techniques

Previously, a High Throughput Experiment (HTE) spectrophotometric method was developed by Dr. Zabula at University of Pennsylvania (UPenn) for fast screening of rare earth metal (REM)(III) unsaturated carboxylates as corrosion inhibitors on cold rolled steel immersed in 0.01 M NaCl electrolyte solutions. This capstone project was conducted in the Solvent-Borne (SB) Undercoat Research and Development (R&D) department at Axalta Coating Systems Coatings Technology Center (200 Powder Mill Rd, Wilmington, Delaware 19803). The goal of this capstone project was to verify the performance of corrosion inhibitors measured by the HTE method, with electrochemical techniques that measure instantaneous corrosion rates of uncoated cold rolled steel panels under identical solution conditions. Potency of REM(III) carboxylates as corrosion inhibitors of uncoated cold rolled steel panels was verified by electrochemical measurements in Phase 1. In Phase 2 of this project, experimental procedure and setup was modified, thus reproducibility in corrosion rates the between instantaneous electrochemical method and the cumulative HTE spectrophotometric method was confirmed. Using the improved electrochemical setup, a prior hypothesis based on the HTE method was confirmed, wherein heteroleptic REM(III) carboxylates can be implemented rather than homoleptic carboxylates, to improve solution stability and to maintain potency of the corrosion inhibitor(s). The electrochemical techniques and experimental procedures herein can be used to find the most compatible/potent REM(III) unsaturated carboxylates as the corrosion inhibitors on coated cold rolled steel within Axalta coatings.