Abstract

The corrosion inhibition of mild steel (MS) in 0.5 M H2SO4 solution by the methanolic extracts of Adansonia
digitata (baobab) fruit pulp extract (ADPE) and A. digitata (baobab) fruit seeds extract (ADSE) was studied
by gravimetric, potentiodynamic polarization, electrochemical impedance spectroscopic, and scanning electron
microscopy (SEM) methods. The weight loss and polarization studies reveal that the corrosion inhibition
efficiency increases with increase in the concentrations of inhibitors ADSE and ADPE. ADSE exhibited high
corrosion inhibitor efficiency (74.5%) for MS. Tafel plots show that baobab fruit extracts act as efficient mixed-
type corrosion inhibitors. The double-layer capacitance (Cdl) and charge transfer resistance (Rct) values derived
from Nyquist plots proved the anticorrosive nature of extracts. The inhibition of corrosion is possibly due to
adsorption of the extracts on MS surface. The adsorption obeys Langmuir adsorption isotherm. The low free
energy of adsorption (∆Gads) values for both the extracts confirmed physisorption on MS surface. The SEM
images confirmed severe surface deterioration of MS exposed to H2SO4 solution in the absence of inhibitors. The
ADSE exhibited high efficiency as green and eco-friendly corrosion inhibitor for MS in acidic medium.