Electroplating of Sn-Zn alloys from aqueous gluconate baths

Electroplating of Sn-Zn alloys onto steel substrates from gluconate baths c ontaining ZnSO4, SnSO4 and Na2SO4 has been investigated under different con ditions of bath composition, current density, pH and temperature. The influ ence of these variables on the potentiodynamic polarization curves, cathodi c current efficiency and composition of the deposit were studied. The resul ts show that the deposition of Sn-Zn alloys from gluconate baths depends gr eatly on the concentration of zinc ions content. The codeposition of Sn-Zn alloys from these baths can be classified as a regular plating system. The surface morphology of deposits was examined by scanning electron microscopy and crystal structure by X-ray. The results show that irrespective of the bath composition and conditions of electroplating, all the deposits were cr ystalline and ave simple mixtures in accord with the equilibrium phase diag ram.