Abstract
The flora of Saudi Arabia comprises about 18 species of Acacia species including Acacia hamulosa Benth. The methanolic extract of the flowering tops of A. hamulosa was tested for its radical scavenging activity toward 2,2-diphenyl-1-pricylhydrazyl (DPPH) radical and the activity was compared with L-ascorbic acid, quercetin and Trolox as standards. The total phenolic content was determined using Folin-Ciocalteu method. In addition the methanolic extract has been evaluated as a corrosion inhibitor for steel in 1 M HCl solution by means of weight loss measurements, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS). Tafel polarization study revealed that extract of Acacia hamulosa acts as a cathodic type inhibitor. Inhibition was found to increase with increasing concentration of the extract of Acacia hamulosa. Values of inhibition efficiency calculated from weight loss, Tafel polarization curves, and EIS are in good agreement. The effect of temperature on the corrosion behaviour of mild steel in 1 M HCl with addition of extract was also studied and thermodynamic parameters were determined and discussed.