Evaluation of corrosion inhibition of brass in chloride media using EIS and ENA

The corrosion behavior of 26000 brass has been studied in 3% NaCl and in artificial seawater using electrochemical impedance spectroscopy (EIS) and electrochemical noise analysis (ENA). Benzotriazole (BTA). gluconic acid sodium salt (GASS) and polyphosphoric acid sodium salt (PP) were evaluated as corrosion inhibitors. While BTA provides excellent corrosion inhibition in both media, PP was not very effective. For GASS maximum corrosion inhibition was obtained at a concentration of 0.01 M. Analysis of the electrochemical noise (ECN) data demonstrated the need for removal of drifts in the potential and current fluctuations during the measurement period that affected the values of the power spectral density (PSD) plots, After trend removal the slopes of the current PSD plots were -2 in the absence of BTA and -1 in its presence. The slopes of the potential PSD plots did not change from their value of -2 due to the addition of BTA. Very good agreement of impedance and spectral noise plots was observed after trend removal for solutions containing BTA. The location index was not found to provide information concerning corrosion mechanisms. Skewness and kurtosis for both potential and current fluctuations had similar values in the absence and presence of BTA that were typical of a normal distribution of the ECN data. (C) 2001 Elsevier Science Ltd. All rights reserved.