2-aminobenzimidazole as corrosion inhibitor for 70-30 brass in ammonia

Abstract

Corrosion of 70-30 brass in 1·0M ammonia solution and its inhibition by 2-aminobenzimidazole (2-ABZ) has been studied from mass loss and galvanostatic polarisation measurements. The effects of inhibitor concentration (10⁻⁶ to 10⁻³ M) and of temperature (293 to 313 K) on inhibition efficiency were investigated. At a given temperature with increasing inhibitor concentration the polarisation curves shift to higher potentials, corrosion potentials shift slightly to the less noble direction, and the Tafel slopes remain virtually constant. The energy of activation is lowered in the presence of the inhibitor. The results indicate that 2-ABZ acts as a mixed inhibitor, does not affect the mechanism of the electrode processes, and inhibits corrosion by blocking the reaction sites. In the presence of 2-ABZ a protective film is formed on the surface of brass. From ir spectral studies the film has been shown to consist of complexes of Cu(II) and Zn(II) with 2-ABZ acting as a bidentate ligand coordinated to the metal through the imino nitrogen (N-H) and azole nitrogen (C=N) groups of the inhibitor.