Adsorption of Cowpea Husk Extract and Corrosion Inhibition at Interface between X80 Steel and Acidic Oilfield Descaling Fluid

Abstract

Cowpea husk is an agro-industrial by-product that can be sustainable and cheaply obtained in large quantities. Ethanol extract of the husks (CWPE) was assessed as a corrosion inhibitor for X80 steel in 1 M HCl at 303 – 333 K under static weight loss and electrochemical conditions, accompanied by functional group (FTIR) and surface morphological (SEM) analyses. The inhibition efficiency of 94.6 % and 85.2 % were obtained at 303 and 333 K. CWPE acts as a mixed type corrosion inhibitor with a major influence on the anodic half-reaction and increases charge transfer resistance while decreasing double-layer capacitance and corrosion current density. Corrosion inhibition is attributed to spontaneous adsorption of CWPE phytocompounds on X80 steel surface best approximated by the Langmuir adsorption model. Adsorption is enabled mainly by O, N, and C=C sites affording surface protection and reduced pitting as observed by SEM. CWPE is a potential alternative corrosion inhibitor for X80 steel in mildly acidic environments.