Enzyme- and acid-extracted sugar beet pectin as green corrosion inhibitors for mild steel in hydrochloric acid solution

Abstract Pectin extracted from sugar beet pulp using enzymatic or acid hydrolysis was evaluated as corrosion inhibitor for mild steel under acidic conditions. Effect of pectin concentration on corrosion rate and efficiency was studied via weight loss and electrochemical measurements. The effect of temperature on corrosion inhibition was studied in temperature range from 298 to 333 K. The thermodynamic parameters of corrosion process such as activation energy, equilibrium constant of adsorption (Kads), and standard free energy of adsorption (ΔGads) were also calculated. Scanning electron microscopy (SEM) coupled with Energy Dispersive X-Ray analysis (EDX) was used to examine the surface of mild steel after corrosion test. The results showed dependence of corrosion efficiency on method of pectin extraction. Enzymatic-extracted pectin showed moderately higher inhibition efficiency than the acid-extracted pectin. Polarization curves indicated that both types of pectin acted as mixed-type inhibitors with predominant inhibition at the cathodic site.