Rapid evaluation of corrosion inhibitors in acidic solution using the coulostatic method

Abstract

A monitoring method for the corrosion rate of metal based on the coulostatic principle and a new mathematical model for the evaluation of Tafel coefficients from coulostatic experimental data are presented in this paper. Different kinds of equivalent circuit models involving R(CR(RL)) and R(RC) have been applied to examine the characteristics of the response curves to coulostatic and AC perturbations. In addition, weight loss and electrochemical impedance spectroscopy (EIS) experiments on Q235 mild steel in 0 . 5 M H 2 SO 4 solutions with and without thiourea as inhibitor have been used to verify the results from the coulostatic method. It was found that the coulostatic technique can not only determine values of R p and C d quickly, but also the Tafel coefficients in the acidic solution with and without inhibitor. Moreover, since coulostatic measurements can always assume R p equal to R t in this system, the corrosion rate calculated by the coulostatic method is free of confusion between R p and R t . This facilitates the rapid calculation of corrosion current density based on the Geary-Stern equation, and provides a simple procedure for the evaluation of corrosion and corrosion inhibitors.CEST/2143

Coulostatic-Based Research on Corrosion Inhibition Mechanism of Three Inhibitors for Hot Dipped Coating Steels

“…We must consider the changes in the state of the metal surface and the drift of E corr . Therefore, the mechanism of action of the inhibitor molecules was explored by using coulostatic method to reflect the anode and cathode process Tafel constant ba, bc and corrosion current density I corr and other important electricchemical parameters [10,11], and combined with changes in the interface electrical properties to study the mechanism of action of the corrosion inhibitor. Rapid screening of inhibitor, to evaluate the inhibition effect of the method to explore the means of coulostatic test.…”