keywords: Corrosion, inhibitors, mild steel, scanning electron microscopy, weight loss
Extract of Brachystegia eurycoma Seed (BES) was investigated as corrosion inhibitor of mild steel in 1M H2SO4 using phytochemical screening, weight loss, scanning electron microscopy (SEM), and fourier transform infrared spectroscopy (FTIR). The analysis of the weight loss results showed that the Inhibition efficiency of the Brachystegia eurycoma seed extract is directly proportional to its concentration and inversely proportional to solution temperature and mild steel contact time in the test solu¬tion. The inhibition efficiency increases gradually reaching a maximum value of 95.53% within the first 24 h at a concentration of 5.0 g/l. The kinetic study shows that the inhibitory action is a first order kinetics with the concentration of the seed extract of Brachystegia eurycoma which is best fitted into the Langmuir adsorption isotherm. Thermodynamic parameters indicated that the adsorption of Brachystegia eurycoma seed extract onto the metal surface was spontaneous, exothermic and supported the physical adsorption process. FTIR results showed that the inhibition mechanism was an adsorption process through the functional groups present in the seed extract. Surface morphology also revealed that corrosion product confirmed the protection offered by the extract on the surface of the metal immersed in the acid media.