The effect of triphenylphosphane on corrosion inhibition of benzotriazole at Ag electrode monitored by SERS in nonaqueous solution

Abstract

The corrosion inhibition behavior of benzotriazole (BTAH) on Ag electrodes and the influence of triphenylphosphane (pph3) were investigated by electrochemical method, in situ surface-enhanced Raman spectroscopy (SERS) and direct electrochemical synthesis of surface complexes in nonaqueous solution. The results indicated that the BTA− ion was coordinated to the Ag surface to form a highly cross-linked surface polymer complex of [Ag(BTA)]n, which suppressed the dissolution and oxidation of Ag effectively. The introduction of a neutral ligand of pph3 blocked the surface coordination processes of BTAH with the Ag electrode. It resulted in a decrease of inhibition efficiency to Ag surface. The ligand of pph3 played a negative role on the corrosion inhibition of BTAH to the Ag electrode. The SERS results were well consistent with the cyclic voltammetry and polarization curves measurements. For modeling, two different surface complexes were prepared in acetonitrile with and without pph3 by direct electrochemical synthesis. A polymer-like complex of [Ag(BTA)]n attached to the Ag surface was obtained in the absence of pph3, which suppressed the dissolution and oxidation of Ag effectively. A new binuclear compound, Ag2(BTA)2(pph3)4, was produced in acetonitrile with pph3 and the final coordination process occurred in solution leading to difficulties in forming a compact surface film, thus decreasing the corrosion inhibition efficiency of BTAH. The role of pph3 and the mechanism were proposed.