The effect of benzotriazole on mass transfer in the corrosion of a copper rotating disk electrode

Abstract

The effect of benzotriazole, BTA, on mass transfer in dissolution-corrosion of the copper rotating disk electrode in 0.02 M Fe(III)–0.5 M H₂SO₄ has been studied by means of atomic absorption spectrometry. The mass transfer coefficient, K, was determined from the slope of ln(C ₀/C)_Fe(III) vs. time plots. In the absence of BTA the corrosion process can be described by the correlation Sh = KR/D = 4.47Re ^0.5. The difference in values between Sh and Sh _Levich, and the change in slope in the Arrenhius plot points to mixed control for the cathodic process Fe³⁺ + 1e⁻ → Fe ²⁺ and charge transfer control for the anodic process, Cu → Cu²⁺ + 2e. The average activation energies were 7.7 kJ mol⁻¹ and 19.5 kJ mol⁻¹ at (500–1500) and (2000–3000) rpm, respectively. At low concentration of BTA the inhibiting action of BTA increases with concentration and with rotation speed. For [BTA] ≥ 5 × 10⁻³ M, the K value, 10⁻⁴ cm s⁻¹, remains constant and is independent of rotation rate. The morphology of the copper rotating disk after corrosion in the absence and presence of BTA was examined using scanning electron microscopy (SEM).