Effect of some Thioureas on the Corrosion and Dezincification of 63/37 Brass in Ammonia Solution

Abstract

The inhibitory action of thiourea and its derivatives, N-phenyl thiourea and diphenyl thiourea, towards the corrosion of 63/37 brass in ammonia solution has been investigated, using weight loss, solution analysis and potentiostatic polarisation techniques. All the inhibitors reduce the dissolution of both zinc and copper, but none of the inhibitors are effective in reducing the preferential dissolution of zinc. All the inhibitors give Langmuir type adsorption isotherms, and shift the corrosion potential towards the more passive region. Thiourea and N-phenyl thiourea act as mixed inhibitors while diphenyl thiourea acts as an anodic inhibitor only.