Abstract

This research aims to investigate the potential of Melocactus curvispinus pulp extract as a “green inhibitor”, focusing on the electrochemical behavior of API-N80 steel in a saline solution (3.5% m/v NaCl) and 1 mol/L H₂SO, with extract concentrations of 5, 10, 15 and 20% (v/v), as an environmentally friendly approach to reducing the use of toxic corrosion inhibitors, which are harmful to both the environment and human health. To achieve this, electrochemical techniques including potentiodynamic polarization, morphological characterization by SEM and photochemical analysis via FTIR with polarity fractionation were employed. The results of the electrochemical measurements showed that the extract acts as a mixed-type inhibitor in both saline and acidic media. In the saline medium achieving a maximum inhibition efficiency of 83.89% at a concentration of 15%, whereas at a concentration of 20%, a reversal of the protective effect was observed, attributed to saturation of the metal/solution interface, which accelerated the corrosion process. In the case of the acidic medium achieving a maximum efficiency of 78% at 20% extract concentration, conforming to the Langmuir isotherm with a physisorption mechanism (ΔGads = -3.09 kJ/mol). SEM revealed the formation of a protective film in both media, which was denser and more compact in the saline medium than in the acidic one, correlating with the observed efficiency levels. FTIR analysis confirmed the presence of alkaloids, coumarins, saponins and pentacyclic triterpenes identified in the phytochemical tests. The research validates the M. curvispinus extract as a functional bio-inhibitor for N-80 steel in both aggressive environments, although its use is limited by industrial volumetric requirements.5_Paredes.png