Effect of cetyl pyridinium chloride on corrosion inhibition of mild steel in acidic medium

The corrosion inhibition behavior of cetyl pyridinium chloride (CPC) on mild steel (MS) in 0.5 M H₂SO₄ solution was examined using weight loss and potentiodynamic polarization method. Different concentrations of CPC (0.000192 M, 0.0038 M, 0.0057 M and 0.0077 M) was used to find the balanced CPC in the acid solution. Among them, 0.000192 M and 0.0077 M of CPC solution showed a corrosion rate of 8.23×10⁻³, 3.52×10⁻⁵ (mm/Year), and the inhibition efficiency of 89.94 % and 96.23 %, respectively, which is lower than the pure acidic solution (0.5 M H₂SO₄). Furthermore, the experimented MS surfaces were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and Atomic Force Microscopy (AFM). FESEM and AFM studies demonstrated the corrosion attack on the MS surface, which is relatively less as compared to the only acid-exposed surface. The SEM-EDX analysis indicates the presence of nitro-group on the MS surface, which might be due to the contribution of pyridinium protonation of CPC. This phenomenon might enhance the corrosion resistance on the MS surface.