Mechanism of zinc electrodeposition in a chloride solution

Impedance spectroscopic measurements of sheet steel under electrogalvanizin g in an acidic solution of zinc chloride as a function of pH, grain-refinin g additive, current density and SEM morphological observations of the elect rogalvanized surfaces, have revealed the electrodeposition mechanism better than other methods, The electrogalvanizing is simply under the mixed contr ol of charge transfer and diffusion. The hydrogen ion acts to inhibit the c harge transfer slightly and to stimulate water decomposition. The grain-ref ining organic additive appears to be adsorbed effectively on the galvanizin g surface and to deactivate growing kink sites of electrocrystallites at lo w current density, resulting in nucleation-controlled deposits and consider able inhibition of electrodeposition. With increasing current density, the electrodeposition becomes controlled gradually under the influence of the d iffusion of zinc ion.