Electrodeposition of gradient zinc alloys

An electrodeposition study of gradient zinc alloys onto steel has been carr ied out using a rotating disc electrode. The effects of rotation speed and potential on the composition of the alloy coatings were studied. The corros ion resistance and adhesion of the gradient zinc alloy coatings were compar ed with those of conventional duplex coatings. The zinc content of zinc-nic kel (Zn-Ni) and zinc-iron (Zn-Fe) deposits increased with increasing rotati on speed and applied voltage. Increasing the rotation speed increased the z inc content in zinc-nickel-phosphorus (Zn-Ni-P) deposits, and both nickel a nd phosphorus declined. The zinc-iron-phosphorus (Zn-Fe-P) system behaved d ifferently in that the zinc content increased with increasing applied volta ge. The corrosion resistance and deposit adhesion for all four gradient zin c alloys were superior to those of conventional duplex zinc alloys.