Effect of potassium persulfate on current efficiency for gold plating

In this study, the effect of potassium persulfate on current efficiency for gold plating was investigated using electrochemical techniques. The current efficiency in the lowcurrent-density range greatly decreased when potassium persulfate was added to the gold plating solution. However, the current efficiency in the high-current-density range did not change with the addition of potassium persulfate. The measured contact resistances of the resulting gold-plated layers showed almost similar values, regardless of the addition of potassium persulfate, suggesting that potassium persulfate does not affect the property of the gold layers. Linear sweep voltammetry and partial polarization curves showed that the persulfate ion was reduced when the noble potential was more than that of the gold ion. Therefore, the current efficiency for gold plating decreased when potassium persulfate was added in the low-current-density range because at such a current-density the reduction of persulfate preferentially occurs.