INVESTIGATION OF CORROSION INHIBITION OF MILD STEEL IN 0.5 M HCL WITH AZADIRACTHAINDICA AND SPONDIAMOMBIN

Abstract

The corrosion behaviour of mild steel in 0.5 M HCl solution in the presence of Azadiracthaindica and Spondiamombin (AS) was investigated using potentiodynamic polarization and weight loss techniques. Pulverized barks of 60 g of each plant were soaked in 1500 ml, 0.5 M HCl for 48 hours, filtered and mixed in the ratio of 1:1 giving a concentration of 400 g/L (serving as 100 % concentration). The AS mixture was then diluted to 20, 40, 60 and 80% (80, 160, 240 and 320 g/L). The weight loss experiment was carried out for 192 hours at ambient temperature (25oC) and corrodant solution without AS served as the control. Potentiodynamic polarization study was carried out using a device called AutolabPotentiostatGalvanostat (PGSTAT101) in the potential range of ±1.5v versus corrosion potential at a scan rate of 0.005 ms-1. The results obtained showed that corrosion rate reduced in the presence of all the concentrations of AS extract investigated. Highest inhibition efficiency of 99.6% obtained was for the polarization measurement why the highest obtained for gravimetric study was 75.39%. Gibb’s free energy of -3.859 kJ mol-1 was obtained, indicating physisorption and the correlation coefficient was 0.996. The study showed that AS was a very good corrosion inhibitor of mild steel in 0.5 M HCl acid.