A Study of Corrosion Inhibition Properties on Mild Steel of an Acridine-2,4 Dinitrophenylhydrazone Derivative in Oil-Field Water

This study evaluated the corrosion-inhibition performance of the acridine-2,4-dinitrophenylhydrazone derivative C₃₅H₃₄ClN₉O₈ for mild steel in oil-field water using gravimetric weight-loss measurements. Physicochemical analysis showed that the water had a pH of 6.8, conductivity of 54,000 μS cm⁻¹, total dissolved solids of 37,000 mg L⁻¹, dissolved oxygen of 4.5 mg L⁻¹, chloride content of 20,000 mg L⁻¹ and sulphate content of 2,775 mg L⁻¹. Mild-steel coupons were exposed to oil-field water containing different inhibitor concentrations for up to 30 days. Inhibition efficiency increased with inhibitor concentration, and the highest value, 33.85%, was recorded at 10 ppm after 18 days. Cumulative weight loss decreased from 2.911 g in the uninhibited medium to 1.972 g at 10 ppm. Temperature-dependent measurements conducted from 303 to 333 K showed that corrosion rate increased with temperature, whereas surface coverage decreased at each fixed inhibitor concentration. The adsorption data conformed to the Langmuir model, with correlation coefficients ranging from 0.9602 to 0.9894. The adsorption constant decreased from 0.1120 mg L⁻¹ at 303 K to 0.0270 mg L⁻¹ at 333 K. The calculated adsorption enthalpy and entropy were −39.90 kJ mol⁻¹ and −149.8 J mol⁻¹ K⁻¹, respectively. Under the tested conditions, the compound provided concentration-dependent but moderate protection of mild steel in oil-field water.