(v13preprint18)Thermodynamic characterisation of mild steel corrosion and inhibition adsorption of Uncaria gambir and catechin in 1 M HCl

摘要

Uncaria gambir, a native Southeast Asia herbal plant has been widely used as an astringent medicine for treatment of spongy gums, tooth acne, diarrheas and sore throat. Previous studies have shown that more than 80 % of gambir extract consist mostly flavan monomer, which is catechin and epicatechin. The anti-oxidant properties exhibit in catechin attracts people to study further of its applications. The effect of both Uncaria gambir and catechin as corrosion inhibitors for mild steel in acidic solution was done using weight loss measurement at various temperatures. The free energy of adsorption ΔGads for both Uncaria gambir and catechin, indicates that the process was spontaneous and physically adsorbed (physiosorption) onto the mild steel surface. The comparison of inhibition efficiency revealed that Uncaria gambir performed more significant than catechin.