Inhibitive action of mangrove tannins and phosphoric acid on pre-rusted steel via electrochemical methods

The inhibitive action of mangrove tannins, extracted from mangrove barks and phosphoric acid, on pre-rusted steel in a 3.5% NaCl solution was evaluated and the inhibitive efficiency was compared with that of mimosa tannins. From the electrochemical studies, the inhibition efficiency of solutions containing 3.0 g L−1 tannins depended upon the concentration of phosphoric acid added and the pH of the solution. At pH 0.5 and pH 2.0, inhibition was greatest with mangrove and mimosa tannins alone, while at pH 5.5 the addition of phosphoric acid alone gave the highest inhibition.