ELECTRODEPOSITON OF SACRIFICIAL COPPER-MANGANESE ALLOY COATINGS AND THEIR PROPERTIES

摘要

Two types of Cu-Mn coatings can be obtained by electrodeposition from simple sulfate solution with the only addition of ammonium sulfate. Crystalline type Ⅰ coatings are grown at low current density, while at high current density, amorphous typeⅡ coatings are obtained. Both type of coatings are composed of metallic Cu and Mn. A small amount of codeposited Cu can stabilize the ductile as-deposited centered tetragonal phase. Amorphous coatings do not show any structural transformation at room temperature. The mechanical and tribological properties of Cu-Mn coatings were also tested. Cu-Mn coatings have a lower friction coefficient than reference Cd coatings. Codeposition of Cu decreases the hardness and modulus effectively. Cu-Mn coatings show a barrier or passive behavior under anodic polarization, while the sacrificial characteristics are still preserved. The corrosion appears uniform; the formation of MnO_2 and Cu_2O may account for the good corrosion performance of the coatings.