Corrosion Inhibition of Mild Steel in Hydrochloric Acid by Tannins Rom Rhizophora Racemosa

Makanjuola Oki, Ebitei Charles, Collins Alaka, Tambari Kayode Oki

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DOI: 10.4236/msa.2011.26079                

Abstract

Studies on the corrosion behaviour of mild steel electrodes in inhibited hydrochloric acid are described. Conventional weight loss measurements show that a maximum concentration of 140 ppm of tannin from Rhizophora racemosa is required to achieve 72% corrosion inhibition. Similar concentration of tannin: H₃PO₄ in ratio 1:1 gave 61% inhibition efficiency, whereas efficiency obtained for phosphoric acid as inhibitor in the same environment was 55%. Corrosion rates obtained over six hours of exposure in 1M HCl solution at inhibitor concentrations of 140 ppm are 2 mA/cm², 2.4 mA/cm², 2.6 mA/cm² and 6 mA/cm² for tannin, tannin/H₃PO₄ and H₃PO₄-inhibited and uninhibited specimens respectively. Natural atmospheric exposure studies revealed that specimens treated in H₃PO₄ resisted corrosion for three weeks, while tannin treated specimens suffered corrosion attack after one week of exposure tests.

Keywords

Inhibitor, Tannins, Corrosion Rate, Rhizophora Racemosa, Phosphoric Acid

Conflicts of Interest

The authors declare no conflicts of interest.

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