The hazardous effects of most synthetic corrosion inhibitors were the motivation for studying the possible use of eco-friendly extract; olive (Olea europaea L) leaf extract, as a scale and corrosion inhibitors for steel surface in brine solution. The antiscale properties of the natural extract were studied using electrochemical impedance spectroscopy (EIS), and chronoamperometry techniques in conjunction with a microscopic examination. The inhibitive characteristics were investigated using EIS and potentiodynamic polarization curve measurements. Mineral scales were deposited from the brine solution by cathodic polarization of the steel surface at -0.9 V (vs. SCE). The mechanism of scale inhibition was attributed to the formation of cytotoxically inactive complex of calcium caffeate which adsorb on the steel surface at an early stage and poisoned crystal nuclei around them. Potentiodynamic polarization curves indicated that the extract inhibits the corrosion of steel by controlling the cathodic oxygen reduction process. The results showed that olive leaf extract can inhibit corrosion of steel and scale build-up under the conditions tested. (C) 2011 Elsevier B.V. All rights reserved.