Effect of Benzotriazole on the Corrosion and Electrodeposition of Copper.

A study has been made of the influence of benzotriazole as a corrosion, inhibitor for copper and brass in atmospheric and immersed environments. The effect of benzotriazole as an addition agent in the copper sulphate-sulphuric acid plating bath has been investigated systematically, with a particular emphasis on the correlation between the structure and properties of the coatings. Benzotriazole has been found to be a good inhibitor and was discovered to act as a weak buffer for copper and brass immersed in acidic, neutral and alkaline solutions. The film, formed by pre-dipping copper into a hot aqueous solution of benzotriazole, increased the corrosion resistance in many solutions and was particularly beneficial in oxidizing and complexing solutions, as well as in decreasing the rate of oxidation in atmospheric conditions up to about 350 C. Benzctriazole was found to have similar inhibitive properties to naphthotriazole and was much better than triazole in several environments. It was established, by using the Stereoscan,that the presence of benzotriazole in the plating solution modified the nucleation and growth of the deposits. With low concentrations adsorption occurred during plating, while with higher additions it was codeposited in a layered structure. In deposits from the plain bath, the grain size decreased while the hardness and tensile stress increased,as the bath temperature was lowered and the current density raised. Deposits from the bath containing benzotriazole had a much smaller grain size and were much harder, the actual hardness varying with the plating parameters in a similar manner to that of the deposits from the plain bath. The internal stress, measured with the Spiral Contractometer, could be tensile or compressive and depended upon the concentration of benzotriazole in the solution and the plating conditions, the range of values being from 164 MN/m[2] tensile to 121 MN/m[2] compressive. The results produced in this work have been analysed in the light of the known theories and correlations produced