Aqueous extract of Argemone mexicana roots for effective protection of mild steel in an HCl environment Gopal Ji 1 • Priyanka Dwivedi 2 • Shanthi Sundaram 2 • Rajiv Prakash 1 Received: 16 September 2014 / Accepted: 19 March 2015 Ó Springer Science+Business Media Dordrecht 2015 Abstract The inhibition effect of aqueous Argemone mexicana root extract (AMRE) on mild steel corrosion in 1 M HCl has been studied by weight loss, Tafel polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy techniques. Results indicate that inhibition ability of AMRE increases with the increasing amount of the extract. A maximum corrosion inhibition of 94 % is acknowledged at the extract concentration of 400 mg L -1 . Polarization curves and impedance spectra reveal that both cathodic and anodic reactions are suppressed due to passive layer formation at the metal–acid interface. It is also confirmed by SEM micrographs and FTIR studies. Furthermore, the effects of acid concentration (1–5 M), immersion time (120 h) and temperature (30–60 °C) on inhibition potential of AMRE have been investigated by the weight loss method and electrochemical techniques. An adsorption mechanism is also proposed on the basis of weight loss results, which shows good agreement with the Langmuir isotherm. Keywords Mild steel  Polarization  Acid corrosion  SEM  Green inhibition Electronic supplementary material The online version of this article (doi:10.1007/s11164-015-2029-y) contains supplementary material, which is available to authorized users. & Gopal Ji gopalji.rs.mst11@itbhu.ac.in & Rajiv Prakash rajivprakash12@yahoo.com 1 School of Materials Science and Technology, Indian Institute of Technology, Banaras Hindu University, Varanasi, India 2 Centre of Biotechnology, Allahabad University, Allahabad, India 123 Res Chem Intermed DOI 10.1007/s11164-015-2029-y