Corrosion inhibition and passivation characteristics of neem leaf oil extracts on mild steel in citric acid media

摘要

Corrosion inhibition properties of neem leaf oil extracts (NLO) on mild steel corrosion in 2.5 M citric acid solution was evaluated through electrochemical technique, weight loss measurement, open circuit potential measurement, optical characterization, macro-image analysis and ATF-FTIR spectroscopy. Data showed NLO had peak inhibition efficiency of 99.55% and 88.88% from potentiodynamic polarization and coupon measurement at 5% NLO concentration. Delayed passivation of the mild steel was observed after metastable pitting. Inhibition effect of NLO was calculated to be anodic type and independent of time and concentration. Thermodynamic stability was observed on the corrosion potential of the mild steel in the presence of NLO compared to to the control sample with significant potential transients. Analysis from ATF-FTIR spectroscopy showed physisorption and physiochemical adsorption of protonated NLO molecules. Macro surface analysis showed severe morphological deterioration of the carbon steel compared to NLO inhibited surface.