The toxicity of most synthetic corrosion inhibitors as well as recent environmental awareness
provides sufficient motivation for the evaluation of natural products as potential alternatives. In
response to this, the present paper presents the results of a series of studies in our laboratory
on the inhibitive effect of selected plant extracts on the acid corrosion of mild steel using
different electrochemical and non electrochemical techniques. The results indicate that all the
extracts inhibited the corrosion process by virtue of adsorption of their phytochemical
constituents on the corroding steel surface and inhibition efficiency improved with
concentration of the active constituents. Synergistic effects increased the inhibition efficiency in
the presence of halide additives. Inhibition mechanisms showed no generalized correlations,
but our observed inhibition efficiencies, in excess of 95% in many instances, is adequate
indication that some of these extracts are suitable candidate materials for the formulation of
effective non toxic and environmentally friendly corrosion inhibiting additives.
Keywords: Steel, corrosion inhibition, plant extracts; phytochemical compounds, non-toxic, Occimum
viridis , Telferia occidentalis , Azadirachta indica and Hibiscus sabdariffa, Mimosa pudica, Moringa
oleifera, Garcinia kola, anodic, cathodic inhibitor, mixed inhibitor, adsorption