Effect of Potassium Dihydrogenpyrophosphate and Boric Acid on the Palladium Deposition from Palladium(II) Sulfate Solutions

Abstract

Effects of potassium dihydrogenpyrophosphate and boric acid for the palladium electrodeposition from the potassium thiocyanatepalladium(II) chloride solution have been studied. The potential for metal deposition in a thiocyanic acid solution containing palladium(II)ion was more positive than that in the absence of palladium(II) ion, with depression of hydrogen evolution. The addition of potassium dihydrogenpyrophosphate to the thiocyanic acid solution containing palladium (II) ion made the potential for the palladium deposition more negative than that in the absence of potassium dihydrogenpyrophosphate. Addition of boric acid made the potential further negative. The potassium dihydrogenpyrophosphate increased the limiting current density for H2 evolution and controlled the pH variation of the. electrode surface. The absence of either potassium dihydrogenpyrophosphate or boric acid caused the formation of a crack in electrodeposit for the palladium deposition. At the surface of the palladium deposition gained from the potassium thiocyanatepalladium chloride solution contaning both potassium dihydrogenpyrophosphate and boric acid, cathode current efficiency increased.