Corrosion protection by poly(3-hexylthiophene)/poly(methyl-methacrylate) coating of cracked 410 stainless steel

Purpose This paper aims to study the corrosion protection of 410 stainless steel (410SS) cracked by fatigue tests. The purpose of this study is to show that using polymeric coatings, it is possible to reduce the corrosion rate in metallic structures in operation. Design/methodology/approach Poly(3-hexylthiophene) (P3HT)/poly(methyl-methacrylate) (PMMA) composite was used as a coating to protect the cracked 410SS in the corrosive environment 0.5 M NaCl at 25°C and 80°C. Physicochemical characterization was carried out by adhesion tests, thermogravimetric analysis, nuclear magnetic resonance and size exclusion chromatography. Surface morphology was studied before and after the electrochemical tests by scanning electron microscopy. Uncoated and coated cracked 410SS were characterized by DC electrochemical techniques: linear polarization resistance and potentiodynamic polarization curves. Findings P3HT/PMMA coating reduced corrosion rate and crack propagation of 410SS in the corrosive medium NaCl 0.5M. The P3HT/PMMA coating increased the polarization resistance by one order of magnitude and decreased the corrosion current density by one order of magnitude, relative to the values obtained with uncoated cracked 410SS. The coating helped to have a less damaged surface and less crack propagation on the cracked 410SS. The feasibility of increasing the useful life of cracked metal structures in a saline environment was demonstrated through polymeric composite coatings. Originality/value In the literature, no works were detected that report the use of organic coatings to protect cracked metals against corrosion. This is the first reported work on the corrosion protection of 410SS in a saline medium using coatings based on P3HT/PMMA.