ALKALOID EXTRACT OF ALNUS NEPALENSIS BARK AS GREEN INHIBITOR FOR MILD STEEL CORROSION IN 1 M H2SO4 SOLUTION

Abstract

Extraction of alkaloids from Alnus nepalensis bark has been successfully carried out, and used as green inhibitor for mild steel corrosion exposed to 1 M H2SO4 solutoin. Corrosion inhibition has been monitored by weight loss measurement and electrochemical methods (open circuit potential method and potentiodynamic polarization method). Alkaloids have been tested by two qualitative chemical analysis: Mayers test and FTIR spectroscpic test. Weight loss measurement was employed to study the inhibitor concentration and immersion time effect. Similarly, temperature effect on inhibition efficiency was also carried out by this method. The corrosion inhibition efficiency with concentration at the various time showed that the maximum efficiency occurs at 3 h for 1000 ppm solution is 71.94 % at 25 C. These results concluded that the inhibition efficiency was incresed with inhibitor concentration. Potentiodynamic polarization for 3 h immersed samples in the presence and absence of inhibitors has been carried out. The maximum efficiency of immersed sample is 90.00 % for 1000 ppm solution. The corrosion potential density was decreased with increase in concentration. The OCP measurement revealed that alkaloids acted as a mixed type of inhibitor. The adsorption isotherm and theromdynamic parameters are calculated and energy of activation (Ea) is found to be 74.48 kJ/mol. The positive value of enthalpy indicated that the reaction involves is endothermic in nature.