ORIGINAL ARTICLE Bio-/Environment-Friendly Cationic Gemini Surfactant as Novel Corrosion Inhibitor for Mild Steel in 1 M HCl Solution Mohammad Mobin 1 • Ruby Aslam 1 • Saman Zehra 1 • Musheer Ahmad 1 Received: 10 June 2016 / Accepted: 26 October 2016 Ó AOCS 2016 Abstract Bio-/environment-friendly cationic gemini sur- factant, ethane-1,2-diyl bis(N,N-dimethyl-N-hexadecylam- moniumacetoxy)dichloride, referred to as 16-E2-16, was synthesized and characterized. Corrosion inhibition effects of 16-E2-16 on mild steel (MS) surface in 1 M HCl solu- tion at 30, 40, 50 and 60 °C were evaluated using gravi- metric analysis, potentiodynamic polarisation and electrochemical impedance spectroscopy measurements. The nature of the protective inhibitor film formed on the MS surface was analysed by SEM, EDAX and FT-IR, while TGA was used to assure the thermal behaviour and stability of the film at high temperature. The formation of [inhibitor-Fe 2? ] on the surface of MS was confirmed by UV–visible spectroscopy. The inhibition efficiency of the studied inhibitor increased with increasing concentration and solution temperature. The compound behaved as a mixed type inhibitor and acted by blocking the electrode surface by means of adsorption obeying the Langmuir adsorption isotherm. Surface active properties and corro- sion inhibition effects of 16-E2-16 in the presence of inorganic (NaI) and organic (NaSal) salts were also investigated and are discussed. Density functional theory calculations have been carried out to correlate the effi- ciency of the compound with its intrinsic molecular parameters. Keywords Cationic surfactants  Gemini surfactants  Application of surfactants  Biosurfactant  Synthesis Introduction The unique mechanical properties combined with eco- nomic viability of mild steel (MS) has made it one of the most important constructional materials in a number of industrial applications including petroleum production and refining, marine applications, chemical processing, con- struction, metal processing and other industries. However, it has the disadvantage of poor susceptibility towards cor- rosion in aggressive environments and needs to be pro- tected to ensure a reasonable life. Among the mineral acids, hydrochloric acid is widely used to remove corrosion products from metal surfaces at temperatures up to 60 °C [1–3]. MS in contact with HCl solution is likely to suffer extensive corrosion damage if used unprotected. Among the several methods available to control acid-induced corrosion, the application of inhibitors has been acknowl- edged as one of the most feasible and practical methods widely used in industry. Among chemical substances used as corrosion inhibitors, organic compounds containing multiple bonds and hetero atoms like N, O and S, which can donate lone pair electrons, have been found to be very efficient in controlling the corrosion of metals in many environments [4–7]. Inhibitors with both O and N atoms in their structural units exhibit higher inhibition efficiencies than those containing only one of these heteroatoms [8, 9]. In recent years, various academic and industrial research groups have been attracted by a comparatively new class of amphiphilic molecules called dimeric or gemini surfactants owing to their low critical micelle concentration (CMC) and much better surface active properties than their Electronic supplementary material The online version of this article (doi:10.1007/s11743-016-1904-x) contains supplementary material, which is available to authorized users. & Mohammad Mobin drmmobin@hotmail.com 1 Department of Applied Chemistry, Faculty of Engineering and Technology, Aligarh Muslim University, Aligarh 202002, India 123 J Surfact Deterg DOI 10.1007/s11743-016-1904-x