3-Hydroxy-2-naphthoylamide as corrosion inhibitor for carbon steel in 1 M HCl

3-Hydroxy-2-naphthoylamide (HNA) was investigated in a 1 mol·L -1 hydrochloric acid solution using various techniques, including weight loss test, polarization curve analysis, electrochemical impedance spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The electrochemical test revealed that the corrosion inhibition efficiency showed a gradual increase with increasing concentration, and achieved maximum inhibitory efficiencies of 94% at a concentration of 10 mmol·L -1 . HNA acted as a mixed-type corrosion inhibitors, primarily inhibiting anodic metal dissolution. The surface analysis of carbon steel using SEM, AFM, and XPS confirmed that the corrosion inhibitors adsorbed onto the metal surface, effectively separating the corrosion medium. The adsorption of the inhibitor followed the Langmuir isothermal adsorption model, further supporting their adsorption behavior on the metal surface.