EFFECT OF HALOGENATION ON YELLOW METAL CORROSION - INHIBITION BY TRIAZOLES

The adsorption isotherm and the corrosion rate profile for tolyltriazo le (TT) and butylbenzotnazole (BBT) were presented as functions of imm ersion time in triazole solution. Formation of a triazole film on a ye llow metal surface was shown to play a major role in corrosion inhibit ion. In the absence of triazole in bulk solution, halogenation was det rimental to TT and BBT surface films. The disruption mechanism was att ributable to chemical decomposition of the adsorbed triazole by haloge n. However, adding TT (> 0.2 mg/L) to the halogen-based biocide soluti on improved stability of the protective TT film significantly. The imp rovement in stability was evident from the nearly unchanged surface co verage and lower corrosion rate. Based on this result, an enhanced TT- intermittent-feed method was developed. The metal surface was passivat ed initially with TT. Addition of halogen-based biocide was accompanie d by a concurrent addition of TT (0. 5 mg/L to 2 mg/L). Results demons trated that the enhanced TT-intermittent-feed method performed better than the initial slug feeding of TT and BBT in inhibiting yellow metal corrosion.