ELECTRODEPOSITION OF PB-CU ALLOY COATINGS FROM GLUCONATE BATHS

Pb-Cu alloy coatings were electrodeposited on steel sheet cathodes fro m baths containing mixtures of lead nitrate, copper nitrate and sodium gluconate. Cathodic polarization, cathodic current efficiency and dep osit composition were determined under different plating conditions. T he results were consistent with the behaviour of a regular plating sys tem with copper being the preferentially depositable metal. The lead ( the less noble metal) content in the deposits increased with increase in current density and concentration of lead in the bath but decreased with increase in bath copper concentration. The structure and morphol ogy of the as-deposited coatings were examined by X-ray, AES and SEM. The results showed that the deposits consist of a mixture of fine crys tals of the two metals and the morphology of the deposits is mainly co ntrolled by the composition of the deposit.