Comparative electrochemical and spectroscopic analysis of the inhibition effect of molybdates and boiled red onion extract on the corrosion of tin in acidic solution

Abstract

The corrosion inhibition efficiency (η%) and its passivation mechanisms of tin in 0.2 M malic acid by two different types of potential inhibitors, boiled red onion skin extracts (BROE) and molybdate (MoO4 2−), were examined and compared. The influence of the two inhibitors was evaluated by using the electrochemical polarization and the electrochemical impedance spectroscopy (EIS) methods. The electrode surface coverage was analyzed employing scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The electrochemical polarization curves revealed that increasing inhibitor concentration led to a significant reduction of the tin corrosion rate. The presence of BROE and molybdates produced inhibition efficiency (η%) values of 93 and 87%, respectively. Electrochemical measurements and surface analysis have shown satisfactory agreement, that both inhibitor compounds effectively inhibited tin corrosion in 0.2 M maleic acid by forming protective inhibiting deposits that hindered the active electrochemical corrosion sites on the tin surface. Comprehensive insights into the corrosion inhibition mechanism of these compounds in a 0.2-M maleic acid environment, through the suggested equivalent circuits, are also provided.