Artemisia oil (Ar) is extracted from artemisia herba alba collected in Ain es-sefra-Algeria, and tested as corrosion inhibitor of steel in 2 M H3PO4 using weight loss measurements, electrochemical polarisation and EIS methods. The naturally oil reduces the corrosion rate. The inhibition efficiency was found to increase with oil content to attain 79% at 6 g/l. Ar acts as a cathodic inhibitor. The effect of temperature on the corrosion behaviour of steel indicates that inhibition efficiency of the natural substance decreases with the rise of temperature. The adsorption isotherm of natural product on the steel has been determined. (c) 2005 Elsevier B.V. All rights reserved.