Application of AA Analysis in Characterization of Aluminum Anodic Coatings Formed on Aluminum Alloys

摘要

A method for a quantitative analysis of the aluminum content in anodic coatings formed on aluminum alloys is developed using atomic absorption spectrophotometry. This method can provide a large quantity of information regarding anodic coatings and anodizing processes, such as Al content, Al_2O_3 percentage and Al_2(SO_4)_3 percentage in an anodic coating. In addition, conversion efficiency, current efficiency and Al~(3+) build-up rate of an anodizing process in the anodizing electrolyte, and the effects of different alloys and operational parameters, as well as bath compositions on the resultant anodic coatings can be calculated. It was found in this study that a higher content of sulfate contributes to the softness of Type II coatings in comparison to Type III coatings, in addition to porosity. This principle is applicable to the anodic coatings on alloy 2024 as well. This investigation also showed that the conversion efficiency in a commercially available anodizing process is around 30 percent higher than the highest value reported previously, and the current efficiency of the process in anodizing alloy 2024 is about 10 percent higher than that of the conventional processes. This f8inding provides a reasonable explanation for the fact that the process requires less decant frequency of the anodizing baths and produces more wear-resistant hard coating on alloy 2024 than do conventional anodizing processes.