A Study On Adansonia Digitata Pulp And Seeds Methanolic Extracts As Corrosion Inhibitors Of Mild Steel In Acidic Media

ABSTRACT

The corrosion inhibition efficiency of Adansonia digitata (baobab) pulp and seeds methanolic extracts on mild steel in acidic media is investigated using different standard corrosion methods at room temperature. Weight loss measurement, Potentiodynamic Polarization and Electrochemical Impedance Spectroscopy (EIS) were applied to evaluate inhibition efficiency in the presence of Adansonia digitata Pulp Extract (AdPE) and Adansonia digitata Seed Extract (AdSE) as corrosion inhibitors. The surface morphological changes were analysed using the Scanning Electron Microscope images. The results revealed that AdPE and ADSE are efficient inhibitors of corrosion of mild steel in different acidic media. The corrosion rates were observed to decrease with increase in concentration of the extracts. Inhibition efficiency (% IE) is comparatively high in HCl compared to H2SO4 and decrease with concentration of acid. The values of % IE were 77.61 and 91.12 in 0.5 M HCl, 76.25 and 85.63 in 1.0 M HCl, 71.83 and 79.22 in 0.5 M H2SO4 and 59.63 and 74.35 in 1.0 M H2SO4 for AdPE and AdSE, respectively. The electrochemical analysis also confirmed that the corrosion current density decreases as the concentration of the extract increases, causing a reduction in the corrosion rate of the mild steel sample. Moreover, Nyquist plots from EIS also proved that as the concentration of plant extracts increases, the charge transfer resistance increases and the double layer capacitance decreases. The inhibitive action of the plant extracts demonstrates that the adsorption of plant extracts is spontaneous, and the physical adsorption follows Langmuir adsorption isotherm. All experiments reveal that AdSE works better as corrosion inhibitor of mild steel in acidic media than AdPE.