Improved statistical analysis of ion chromatography data from acids for aluminum anodizing solutions

• Published in: Journal of Chromatography A 1996-07, Vol.739 (1), p.163-166
• Main Author: Sopok, Samuel
• Format: Article
• Language: English
• Subjects: Oxalic acid; Process monitoring; Statistical analysis; Sulfuric acid
• ISSN: 0021-9673
• DOI: 10.1016/0021-9673(96)00269-5

Process monitoring and control of sulfuric and oxalic acids in aluminum anodizing solutions is necessary for producing high quality metal coatings with increased corrosion, wear and abrasion resistance. The production of military armament system parts requires narrow aluminum anodizing solution acid tolerances that increase the need for process monitoring and control. Ion chromatographic analysis is the method of choice used for these military applications. There is significant dispersion in this ion chromatographic data relative to the narrow operating tolerances. An improved ion chromatographic-statistical analysis method reruns/tests data until a specimen's results drop below a dispersion threshold relative to the narrow aluminum anodizing solution acid tolerances. This method provides acceptable process monitoring and statistical control of narrow operating tolerance aluminum anodizing solutions required for high quality military production coatings. The resultant means and improved 95% confident precisions for typical aluminum anodizing solutions are 160.0 ± 1.9 g/l of sulfuric acid and 16.0 ± 0.8 g/l of oxalic acid, which are both an improvement by more than a factor of two over simple 95% confident precisions.