Green corrosion inhibitor for mild steel extracted from soybean leaves

Abstract

The use of green-soluble inhibitors in the corrosive medium as alternatives to traditional inhibitors has increased due to the toxicity of the commonly used substances. These novel substances are selected owing to their low cost, ease of application as well as maintenance, and low environmental risk. This work aims to evaluate ethanolic-water extracts from post-harvest soybean (Glycine max) by-products as corrosion inhibitors for mild steel in an aggressive medium of sodium chloride. Soybean extracts were obtained by percolation at a controlled flow rate and temperature. To evaluate the anticorrosive efficiency, polarization curves of AISI 1030 steel were carried out at 1 and 7 days of immersion with different concentrations of the soybean extract. Weight loss measurements were carried out alongside potentiodynamic measurements. The steel samples were analyzed by scanning electron microscopy. The soybean extracts obtained reduced the corrosion rate of the steel, showing an efficiency of 30% at day 1. The inhibition efficiency increased up to 80% after 7 days of incubation with 2000 ppm of the extract. A Langmuir adsorption model was fitted to weight loss measurements. K_ads and ΔG_ads obtained from the model were characteristic of physisorption. The corrosion potential was shifted toward more negative values, classifying the ethanolic-water soybean extract as a cathodic inhibitor. The steel surface for the samples incubated with 2000 ppm of soybean extract was greatly improved showing significantly fewer agglomeration of corrosion products. Soybean leaves are a promising by-product useful to produce ethanolic-water extracts to be used as green corrosion inhibitors.

Keywords:

• Agricultural waste
• corrosion inhibitors
• Glycine max
• Langmuir adsorption
• percolation
• vegetable by-products

Acknowledgments

This work was supported by the National Scientific and Technical Research Council (CONICET) (Grant number 11220210100406CO). We thank Dr. Silvia Ceré, Dr. Beatriz Valcarce, and T.P.A. Sebastián Rodríguez (National Scientific and Technical Research Council – CONICET) for providing the facilities and advising on the development and fine-tuning of electrochemical measurements. To T.P. Roberto Senus (CONICET) and J.T.P Juan. J. Peralta (University of Mar del Plata – Faculty of Engineering) for collaborating in assembling the percolator and preparing the samples tested. We also thank Miss María Paz González Chapur and her family for providing the soybean leaves.

Author contributions

Alfonso Pepe: Methodology, Formal analysis, Data curation, Validation, Visualization, Writing – Original Draft, Writing – Review & Editing.

Florencia R Tito: Writing – Review & Editing, visualization, formal analysis.

Alejo D. Mandri: Writing – Review & Editing, visualization.

Ricardo C. Dommarco: Writing – Review & Editing, Funding acquisition.

Andres Pepe: Investigation, Project Administration, Conceptualization, Writing – Original Draft.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author upon reasonable request.