Evaluation of the inhibitory effect of methylene blue dye on the corrosion of aluminium in hydrochloric acid

The effect of methylene blue (MB) dye on the electrochemical corrosion of aluminium in HCl solutions was studied using gravimetric techniques at 303 and 333 K. The results indicate that MB acts as an inhibitor in the acidic corrodent. The inhibition efficiency was observed to be sensitive to acid concentration and increased with an increase in MB concentration but decreased with rise in temperature. Synergistic effects increased the inhibition efficiency on addition of halides namely: KCl, KBr and KI. The experimental data were corroborated with the Langmuir as well as Flory–Huggins adsorption isotherms. The activation energy values of 19.39 and 30.53 kJ mol−1 calculated for the corrosion process in the absence and presence of MB, respectively, suggest that the inhibitor molecules are physically adsorbed on the Al surface.