Electrochemical and theoretical studies of 1-(pyridyl-2-azo)-naphthol-2 for control of corrosion of mild steel under H2SO4 environment

Abstract

Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) methodologies were employed to conduct electrochemical investigations of 1-(pyridyl-2-azo)-naphthol-2 (PAN) on MS (Mild Steel), with the aim of evaluating its corrosion mitigation properties. The results of these analysis demonstrate that the presence of PAN leads to effective corrosion mitigation of MS. Its efficiency to inhibit corrosion is enhanced on increasing of concentration and the efficiency attains the maximum of 97.8 % at 10⁻³ mol L⁻¹. The change in value of E_corr less than 85 mV indicates that PAN behaves as a mixed type inhibitor. The mitigation has been thus caused by the development of a protective film by adsorbing PAN on MS. The adsorption process is best suited to Langmuir’s isotherm. Chemisorption and inhibition is strengthened by the synergetic effect between anions and PANH⁺. EIS studies reveal that the charge transfer resistance (R_t) rises from 8.4 Ω cm² for H₂SO₄ to 61.1 Ω cm² for 10⁻³ M PAN while the value of double layer capacitance (C_dl) falls from 174.66 × 10⁻⁴ F cm⁻² to 10.26 × 10⁻⁴ F cm⁻² at 10⁻³ M PAN. This confirms the inhibition of corrosion of MS. The result of Fourier transform infrared suggests the involvement of electron-rich groups such as N, O and aromatic π-electrons in adsorption. Monographs of Field emission scanning electron microscopy display the development of the coating of PAN on MS. Density functional theory studies supplement the electrochemical findings. Thus, the studies carried out in this paper prove that PAN can behave as an excellent inhibitor of MS in acid media.