The inhibiting action of some polyethylene glycols on carbon steel corrosion, using 3N sulphuric acid as corroding solution, was evaluated by the weight loss method and polarization and impedance spectroscopy techniques. In order to study the effect of polyethylene glycol structure on the inhibition efficiency, different molar weights (200-10,000 g mol(-1)) were selected. This work has demonstrated that the polyethylene glycols have an inhibition effect on the corrosion process and the inhibition efficiency is more than 90%. It was shown that polyethylene glycol is adsorbed physically on carbon steel in acid medium. © 2005 Elsevier B.V. All rights reserved.