Corrosion fatigue is an accelerated failure mechanism in metallic components and coated systems, where the effectiveness of the polymer coating is determined by the structural integrity and adhesion at the coating/substrate interface. This study investigated the corrosion fatigue interaction in AISI 410 steel with and without a poly(3-hexylthiophene)/poly (methyl methacrylate) (P3HT/PMMA) coating exposed to a 3 wt.% NaCl solution under four stress levels ∆σ at room temperature. Electrochemical noise (EN) was recorded during the test, the surface and interface were characterized using scanning electron microscopy (SEM), and the mechanical behavior was quantified using da/dN vs. ∆K and σ vs. N curves. The coated samples exhibited a wider potential range (≈±400 mV) than the uncoated steel (≈±200 mV), indicating localized electrochemical activity under the coating. SEM observations revealed microblisters at low stress levels and coating cracking at high stress levels, with localized substrate exposure, slip bands, and microcracks. Overall, the results showed that the corrosion fatigue is governed by electrochemical activity under the coating and cathodic delamination, which reduces adhesion, locally exposes the steel, and causes the initiation and propagation of cracks.
Mirafuentes et al. (Tue,) studied this question.