Abstract

Corrosion inhibition of stainless steel (AISI 316L) by Argemone mexicana (AM) leaf extracts has been studied in hydrochloric acid solution using weight loss, gasometric, electrochemical and surface examination techniques. Results from weight loss measurements revealed an increase in inhibition efficiency with increasing temperature and inhibitor concentration which indicates that AM leaf extracts sufficiently inhibits corrosion of stainless steel through chemisorptions of its constituent molecules. Hydrogen evolution results show that the inhibitor appreciably reduced the volume of hydrogen evolved which implies an obstruction of the cathodic reaction and reduction of corrosion rate. Data obtained from the potentiodynamic polarization scan revealed that AM leaf extracts shifted corrosion potentials of AISI 316L to more positive potential with increasing inhibitor concentration indicating a predominant anodic protection with passivation enhancing capabilities. Surface elemental analysis revealed that the formed corrosion products on the steels’ surface included heteroatom from the leaf extract which confirms that inhibition action was through adsorption of AM leaf extracts’ constituent molecules on the surface of the metal via complex chelating ligands. Adsorption of the leaf extract was seen to obey Langmuir isotherm at high temperature and obtained thermodynamic parameters were discussed.

Key words: Adsorption Passivation Stainless steel Natural products Corrosion inhibition Argemone mexicana