Exploring the role of passivating conversion coatings in enhancing the durability of organic-coated steel against filiform corrosion using an electrochemical simulated approach

This study investigates the effectiveness of conversion coatings (CCs) in mitigating filiform corrosion (FFC) on acrylic-coated steel substrates, with a specific focus on iron phosphatizing and trivalent chromium conversion coatings. Aiming to evaluate the effectiveness of a simulated electrochemical approach introduced in a previous publication, several parameters are determined through an approach involving potentiodynamic polarization curves and zero resistance ammeter on bare CCs. These experiments are conducted in test solutions designed to replicate the electrolytic conditions the substrate encounters undergoing FFC. Similar measurements are collected in neutral testing solutions and the outcomes of the two approaches are discussed regarding the performances of the organic coated sample. The electrochemical evaluation of CCs highlights their potential to reduce the driving forces and nucleation tendency. However, for the steel coated with acrylic paint, while CCs reduce the initiation sites for delamination, they have limited impact on filament propagation.