ELECTROPLATING OF SOME TIN ALLOYS FROM AQUEOUS SOLUTIONS

Abstract

In industrial applications, components can be coated usmg various methods. One of these methods which widely used is electroplating. Direct applications of metal and alloy coatings using electroplating has considerable advantages. The process 1s significantly cheaper. The present thesis was devoted to investigate the electroplating of Sn-Ni alloys from the acid chloride bath onto mild steel substrates. In order to achieve this purpose, it was important to study the electroplating of the parent metals, individually (Sn and Ni) from acid chlorid' e baths under similar conditions. The present work can be divided into three parts.

Part (1):

This part aimed to present the optimum conditions for producing a smooth, bright and adherent tin coating onto mild steel • from acidic stannous chloride bath. A detailed study has been made for the influence of some additives, concentration of SnClz, temperature and current density on potentiodynamic cathodic polarization, cathodic current efficiency and structure of the deposits.

The cathodic polarization curves are characterized by the appearance of limiting current plateau. At more negative potentials, the limiting current of tin deposition increases rapidly as a result of simultaneous evolution of hydrogen gas. The limiting current density and hence the rate of tin deposition increases with increasing the concentration of SnClz, but decreases with increasing the bath