Corrosion Inhibition of Carob Pod Pulp (Ceratonia siliqua L.) on Carbon Steel Surface C38 in Hydrochloric Acid.

The effect of C. siliqua pulp corrosion inhibition on carbon steel has been studied by gravimetric testing and electrochemical methods. In this study, two raw extracts were prepared from the pod pulp of C. siliqua: the first is methanolic and the second is aqueous. The UHPLC/DAD analysis indicated gallic acid's presence in the extracts (methanolic and aqueous) of C. siliqua as a major compound. The inhibition results achieved revealed that the aqueous extract with gallic acid had a good anticorrosion activity with an inhibition rate of 91.32% at 3 g/l for a temperature of 323 K. Potentiodynamic polarization was performed in 1 M HCl without and with different concentrations of C. siliqua extracts clearly proves that inhibitor extracts behave as mixed type. Adsorption of this inhibitor for different extracts studied on the surface of the carbon steel obeys Langmuir adsorption with negative values of Δ G ads ∘ , suggesting a stable and spontaneous inhibition process.