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The study investigated the effect of sebacate as a corrosion inhibitor for acrylic-coated steel. Specifically, it examined its impact on mitigating a frequent case of paint delamination, known as filiform corrosion (FFC), through a chosen weathering test designed to stress the degradation of the produced samples. Sebacate was demonstrated to be an efficient organic molecule for enhancing the corrosion resistance of steel. This efficacy was evaluated through electrochemical characterization based on electrochemical impedance spectroscopy measurements and potentiodynamic polarization curves, including the application of an FFC susceptibility prediction methodology based on measurements obtained in FFC-simulated electrolytes. An inhibition efficiency of 98% was measured in near-neutral saline solutions compared to conditions lacking inhibitor presence. During FFC simulation, the primary effect observed was associated with a reduction in cathodic activity evolution. Furthermore, a significant reduction in corrosion creep evolution of 35% was found. These experimental findings aligned closely with the outcomes projected by the simulated investigations. [ABSTRACT FROM AUTHOR]

Organic coatings delamination and corrosion pose an ongoing challenge in materials science. This review explores the knowledge of corrosion mechanisms in painted steel structures up to date, focusing on filiform corrosion (FFC) investigating its mechanisms, and discussing available prevention strategies alongside their suitability. First reported in the 1940s, FFC garnered significant attention in the subsequent decades, particularly in the study of coated aluminum, and very recently magnesium alloys. However, its consideration as a component of steel degradation remained comparatively limited during this period. Despite advancements, comprehensive analysis of FFC has been infrequent, prompting a call for an updated critical analysis. This survey emphasizes the necessity for organized FFC mitigation strategies, discussing alternatives and emerging trends. It underscores FFC's potential role as a precursor to general corrosion, emphasizing the economic implications of aesthetic damage. This review aims to fill gaps, assess current knowledge, and pave the way for future research in the realm of organic-coated steel corrosion. [Display omitted] • Filiform corrosion is a dramatic failure mechanism in organic-coated steel. • The coating delamination is verified to be driven by the anodic corrosion reactions. • The metal-paint interface is subjected to a harsh chemical environment discernible between anodic and cathodic sites. [ABSTRACT FROM AUTHOR]

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. • Employing conversion coatings shows promise as an effective strategy to mitigate filiform corrosion on painted steel. • An electrochemical simulation approach can be applied to anticipate the performance of inorganic coatings. • Simulated quantitative data are deliberated in reference to the actual corrosion resistance. [ABSTRACT FROM AUTHOR]

A new approach to studying the mechanism of filiform corrosion in organic coated steel based on the scanning vibrating electrode technique (SVET) and micropotentiometry (potentiometric SECM) is presented. The electrochemical activity of the process under the coating is evaluated by mapping the ionic current densities emanating from some artificial defects made in specific locations of the filament identifiable thanks to the transparency of the coating. In addition, antimony tips are employed to investigate the pH changes associated to the different corrosion reactions at the metal-paint interface. Local pH levels associated to anodic and cathodic regions are determined along the filament. [Display omitted] • Anodic and cathodic areas of filiform corrosion on organic-coated steel were identified by SVET. • The activity in the head confined into the "V-shape" morphology resulted anodic and the entire length of the tail cathodic. • Scanning micropotentiometry with an antimony microelectrode allowed local pH distributions in the filament to be measured. [ABSTRACT FROM AUTHOR]