GALVANIC BLACK ANODIZING ON MG-LI ALLOYS

A process of galvanic black anodizing on Mg-Li alloys was studied. The influence of various operating parameters, namely galvanic current density, voltage, pH, electrolyte concentration, operating temperature, anodizing time and heat treatment on the anodic film formation have been investigated to optimize the process. The deposits were characterized by optical and scanning electron microscopy, adhesion tests, corrosion studies, thickness measurement and microhardness evaluation. The space worthiness of the coatings has been evaluated by humidity, thermal cycling and thermo-vacuum tests and measurement of optical properties. The results of all these studies are clearly indicative that the black anodizing process described herein is extremely suitable for ground, as well as space, applications.