ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Corrosion inhibition: a study through alkyl chain length in thioureas

Venkata Muralidhar K, Dharmendr Kumar, and Vinay Jain

TCS Research, Tata Consultancy Services Limited, Pune, India

E-mail: venkatamuralidhar.k@tcs.com

Received: 4 August 2025  Accepted: 28 April 2026

Abstract:

A holistic investigation into the effect of chain-length in thioureas, revealed corrosion mode change (uniform-localised-uniform) phenomena, showing the populating effects and patchy coverages of various homologues at different concentrations. This work clearly demonstrates that addition of alkyl chains stabilizes the adsorbed layer. Potentiodynamic polarization and electrochemical impedance studies reveal a transition in inhibition mechanism, with increasing chain-length. Phase angle of Bode plot shows a clear signature for onset of impervious film formation, hence it can be useful in high throughput screening of molecules. Impedance response of DPTU hinted multiple equivalent circuits for Nyquist plots, however, the applicable circuit could be established using Bode plot, making it a powerful combination to model the system, in case of ambiguity. Unlike the lower homologues, DBTU being the best inhibitor, induces a negative charge on metal surface, hinting a screening parameter. Compared to lower homologues, DBTU follows a different mechanism to inhibit the corrosion. In summary, this work captures several nuances in behaviour and evaluation of thioureas i.e. small molecule substituted with increasing alkyl chain lengths. Understanding the role and contribution of alkyl chains to inhibition would take us one step closer to the easier design of efficient inhibitors.

Keywords: Thioureas; Chain length; Surface charge; Corrosion mode; Inhibition

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04984-2

Chemical Papers 80 (8) 9763–9777 (2026)