Evaluating Corrosion Inhibitors with the Help of Electrochemical Measurements Including Electrochemical Frequency Modulation
Abstract
Electrochemical Frequency Modulation (EFM), cyclic polarization scans, potential noise measurement and long-term exposure tests have been used to evaluate the effects of green tea and tobacco against corrosion. In this work, various corroding environments were used for brass, aluminum and carbon steel materials. The level of corrosion protection by green tea and tobacco was compared with hexamethylene diamine (C6H16N2) for brass and sodium nitrate (NaNO3) for aluminum. The application of EFM for corrosion inhibitors has been investigated by comparing the results of EFM with different other tests. The results indicate that corrosion rate, causality factor 2 and anodic Tafel parameter can be used to evaluate and compare the performance of corrosion inhibitors. Green tea and tobacco do not always protect the chosen metals better than well-known corrosion inhibitors and mostly the level of protection is lower. Green tea was found better corrosion inhibitor than tobacco for brass in acidic environment. EFM technique applies a potential perturbation signal composed of two sine waves to generate a current response at more frequencies than the applied signal. As the corrosion phenomenon is nonlinear in nature, the ac-response will contain components at harmonic and intermodulation frequencies. Corrosion behavior can be studied by analyzing these nonlinear current components.