The role of 316 SS surface finishes in enhancing corrosion protection of conducting polyaniline coatings

Abstract

In the context of polymer-based anticorrosive coating, a surface finish strongly influences the adhesive and protective performance of polymer molecules on the metallic surface, particularly stainless steel (SS) as immersed in the simulated seawater. To achieve that, the ground 316 SS surface is treated by immersing it in a 1 M H₂SO₄ solution within 1 hour before polyaniline (PANi) is coated using a spin coating technique. This method generates effectively a thin, uniform layer on the SS substrate with controllable thickness. The study aims to evaluate the effects of acid-based surface treatment on the adhesion and protective performance of the PANi coating. In this study, surficial characterizations of the coated samples are analyzed using scanning electron microscopes (SEM), atomic force microscope (AFM), contact angle (CA), and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). The results observed indicate that the PANi-coated samples reach a CA of 78 and 90° for the untreated and acid-treated surfaces, respectively. Electrochemical results show that the PANi coated/treated 316 SS surface in 3.5 wt.% NaCl solution has the highest pitting potential of 469 ± 20.2 mV_Ag/AgCl, with a protective efficiency up to ∼94.7%. This advanced behavior is primarily attributed to the formation of a thin film on the 316 SS surface, including a passive oxide layer of SS as a buffer layer and a PANi layer, after treatment in the 1 M H₂SO₄ solution and spin coating respectively. Therefore, the work suggests an effective way to improve the adhesion and protective performance of the PANi coating on the 316 SS in various applications.