Enhancement of the corrosion barrier properties of epoxy coatings through the incorporation of TiO2 and Sulfosalicylic acid doped poly(o-ethoxyaniline) applied onto 420SS in 3.5 wt.% NaCl solution with pH 4.5

The present work focuses on the development of advanced epoxy coatings based on poly(o-ethoxyaniline) (POEA) doped with nano-TiO${}_2$${}_2$ and sulfosalicylic acid (SSA), designed to enhance the corrosion resistance of 420 stainless steel (420SS) compared with conventional zinc phosphate (ZP) coatings. The synthesized coatings were characterized by FTIR spectroscopy, contact angle (CA) measurements, and SEM observations. Their protective performance was further evaluated in a 3.5 wt.% NaCl solution at pH 4.5 using electrochemical techniques, including open-circuit potential (OCP), linear polarization resistance (LPR), potentiodynamic polarization (Tafel curves), electrochemical impedance spectroscopy (EIS), and long-term immersion tests. The POEA-SSA/TiO${}_2$${}_2$ epoxy system exhibited significantly higher corrosion resistance (5-fold), corrosion current density reduced by 50-fold, impedance increased by 100% than ZP, mainly due to the formation of a stronger passivation layer and the contribution of an auxiliary cathodic process between the emeraldine and leuco forms of POEA. Overall, the results highlight the potential of POEA-SSA/TiO${}_2$${}_2$ modified epoxy coatings as durable protective layers for 420SS, offering a practical alternative to conventional ZP for storage tanks operating in acidic salt environment.