A process of integral black anodizing on magnesium alloys

摘要

The inherent lightness and good strength-to-weight ratio of magnesium alloys has focused attention to their increasing applications in aerospace and allied fields. Magnesium is a reactive metal. It forms oxide carbonate film when exposed to atmosphere. Many protective treatments are applied to magnesium components. Most of them do not possess adequate corrosion resistance in excessive exposure and, therefore, require the application of a secondary coating like paint to achieve the requisite corrosion resistance.Black coatings with high solar absorbtion and infrared emittance are important for passive thermal control systems, and also in optical devices to avoid reflections. The present invention descrlbesaprocess of galvanic integral black anodizing on magnesium alloys where an anodic thickness of 1-25 pms can be obtained with a microhardness better than 100 VHN. These coatings provide solar absorption and infrared emittance of the order 0.92 and 0.90, respectively. These can be utilized as an excellent thermal control surface to improve heat radiation characteristics.