Adsorption of 5-Phenyltetrazole on Iron and Its Inhibition of the Dissolution of Low-Carbon Steel in a Neutral Solution

N. P. Andreeva^a, L. P. Kazanskii^a, I. A. Selyaninov^a, Yu. I. Kuznetsov^a, and V. A. Ostrovskii^b

^a Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Moscow, 119991 Russia

^b St. Petersburg State Technological University, St. Petersburg, Russia

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Received July 21, 2008

Abstract—The anodic behavior of St3 steel in a neutral borate buffer solution containing various concentrations of 5-phenyl (PTA) and aggressive sodium chloride additives and the adsorption PTA on the surface of pure iron are studied. Ellipsometry is used to show that the adsorption of PTA begins at concentrations of less than 10^–6 mol/l, which is three orders of magnitude lower than that for an inhibitor such as benzotriazole (BTA). It was shown by X-ray photoelectron spectroscopy that the PTA adsorption is reversible at low exposures of samples in a solution. PTA forms a layer more than 1 nm thick only upon the exposure of samples in the solution for more than 48 h. PTA can reduce the passivation current, though less effectively than BTA. PTA hampers the local depassivation of steel more effectively than BTA.