AbstractThe use of inhibitors is one of the most practical modern methods in preventing and protecting against metal and alloy pipe corrosion. Exploring such additional inhibitors, particularly of natural origins, has become a key area of research. The present work, thus, evaluates the extract of a desert plant fruit, endemic to northern Chile, called Chañar (Geoffroea decorticans), as an inhibitor for the corrosion of A36 steel under a saline environment. Extract inhibition efficiency was evaluated by mass loss, polarization curves, and electrochemical impedance spectroscopy, and surface morphology of the steel after assays was analyzed by scanning electron microscopy. Results showed the formation of a smooth surface on the steel in the presence of the extract and a rough surface in the absence of the extract; also, polarization curves indicated an inhibition efficiency of approximately 82% at a concentration of 200ppm extract, corroborated by electrochemical impedance spectroscopy. The adsorption of the extract on the steel surface follows Langmuir's isotherm model, for which thermodynamic parameters suggest a physisorption mechanism.