84. Surface Treatments for Magnesium Alloys
Xuecheng Dong: Singapore Institute of Manufacturing Technology, Singapore
84.1 Introduction
84.2 Cleaning
Mechanical Cleaning
Chemical Cleaning
Acid Pickling
Fluoride Anodizing
Chemical Conversion Coating
Principles of Chemical Conversion Coatings
Chromate Conversion Coatings
Chromate-Free Conversion Coatings
84.3 Anodizing Methods
Principles of Magnesium Anodizing
Hard Anodizing
PEO Process
84.4 Sealing and Finishing
Sealing
Organic Coatings
Primers
Top Paints
Testing Methods for Treatment Evaluation
84.5 Summary
References
Abstract
Magnesium and its alloys have been found to have a variety of industrial applications owning to their high strength-to-weight ratio. The strength of magnesium alloys is comparable with that of aluminum alloys or steels; however, their corrosion resistance when exposed to severe conditions is relatively weak. Surface treatments are applied to magnesium and magnesium alloy articles to enhance their corrosion resistance and appearance. This chapter covers two classes of treatment for magnesium alloy surfaces for moderate to severely corrosive environments: (1) chemical treatments and (2) anodic treatments, followed by sealing and organic coatings. Necessary cleaning procedures, including mechanical cleaning, chemical cleaning, pickling, and fluoride anodizing, are described.