Electrochemical and computational studies of proline and captopril as corrosion inhibitors on carbon steel in a phase change material solution

Abstract

In this paper, electrochemical and surface analysis methods were used to study the corrosion inhibition performance of proline and captopril on 1045 carbon steel in phase change materials (PCMs). From the electrochemical impedance spectroscopy test results, both proline and captopril inhibitors have a corrosion inhibition effect on 1045 carbon steel in PCM solution, but captopril inhibitors (concentration=0.0005 mol·L-1) have a better inhibition efficiency (ηmax=92.73%) than that of proline. The results of the potentiodynamic polarization tests show that both proline and captopril are mixed type corrosion inhibitors. Field emission scanning electron microscopy (FESEM) and contact angle test results show that captopril inhibitors can effectively reduce the corrosion degree of carbon steel in PCMs. The inhibition mechanism of proline and captopril inhibitors was analysed by theoretical calculations. Both corrosion inhibitor molecules can adsorb on the Fe(1 1 0) surface, among which N atoms, S atoms and-COOH groups are the main sites of adsorption activity. In addition, the diffusion coefficients and surface concentration profiles of H2O molecules and Cl-ions in the two corrosion inhibition systems were studied by a molecular dynamics simulation, which verified that captopril corrosion inhibitors have good corrosion inhibition effects.