Evaluation of Aqueous Extract of Mandevilla fragrans Leaves as Environmental-Friendly Corrosion Inhibitor for Mild Steel
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Evaluation of Aqueous Extract of Mandevilla fragrans Leaves as Environmental‑Friendly Corrosion Inhibitor for Mild Steel in Acid Medium Marcelo T. G. de Sampaio1 · Caio Machado Fernandes1 · Gabriela G. P. de Souza1 · Eliane S. Carvalho2 · Javier A. C. Velasco3 · Júlio César M. Silva1 · Odivaldo C. Alves1 · Eduardo A. Ponzio1 Received: 5 June 2020 / Revised: 25 September 2020 / Accepted: 10 November 2020 © Springer Nature Switzerland AG 2020
Abstract The Mandevilla fragrans leaves extract was evaluated as an environmental-friendly corrosion inhibitor for mild steel in 1 mol L−1 HCl. The inhibitive properties of the extract were tested by gravimetric measurements, polarization curves, linear polarization resistance, and electrochemical impedance spectrometry. The performed experiments showed a good correlation with each other and, using a concentration of 0.800 g L−1, an average anti-corrosion efficiency of 94.1% was reached. The mechanism of inhibition is based on the adsorption of molecules present in the extract on the steel surface generating a layer that protects the surface-to-corrosion process. The surface analysis of the material in the inhibitor presence in aggressive medium using atomic force microscopy sustains the surface protection by the inhibitor adsorption. The study of the adsorption isotherms showed that the Langmuir model is the most adequate one. Keywords Environmental-friendly inhibitor · Mandevilla fragrans · A36 mild steel · Gravimetric tests · Electrochemical tests
1 Introduction Metallic corrosion is the cause of several expenses that directly impact the economy, besides being the cause of accidents and environmental impacts [1]. Mild steel is one of the most widely used metallic materials in industries due to properties such as hardness and ductility, along with having low economic cost. However, this material does not have a good corrosion resistance and several industry operations occur in corrosive media. An example of those is the usage of hydrochloric acid in acid pickling processes [2–4]. In this * Eduardo A. Ponzio [email protected] 1
Laboratório de Materiais da UFF, Grupo de Eletroquímica E Eletroanalítica, Instituto de Química, Universidade Federal Fluminense, Niterói, Rio de Janeiro 24020‑141, Brazil
2
Laboratório de Farmacognosia ‑ Faculdade de Farmácia, Universidade Federal Fluminense, Niterói, Rio de Janeiro 24241‑000, Brazil
3
Laboratório de H2S, CO2 e Corrosividade (LAH2S), Instituto Nacional de Tecnologia, Rio de Janeiro 20081‑312, Brazil
kind of operation, there is a need for surface protection to increase the useful life of the metallic material [5]. One of the most usual protection methods for different types of alloys is the application of inorganic or organic compounds as corrosion inhibitors. These compounds can be classified according to their operation, where the most common are anodic, cathodic, and adsorption inhibitors [6, 7]. In the past, chromates were widely used as inorganic inhibitors, but these compounds are highly toxic, motivating
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