6. Zn-Mn coatings

6.1 Elaboration

The main interest in Zn-Mn coatings lies in the fact that manganese is able to provide cathodic protection to both zinc and steel. However, given the difference between the electrochemical potentials of zinc and manganese, they cannot be deposited simultaneously, and an additive is needed to bring the electrodeposition potentials closer together.

Zn-Mn codeposits have mainly been the subject of development work, without being transferred to industrial applications, although their excellent corrosion resistance and paintability are widely recognized.

Several electrolyte formulations are reported in the literature, namely :

• sulfate-based without additives