Comparing hydrogen testing methods for wrought aluminum

In this study on selected wrought aluminum alloys, several commonly used methods for determining hydrogen were compared and verified with regard to accuracy, reproducibility, and process-related limits. The two direct methods studied—the AlScan and CHAPEL (continuous hydrogn analysis by pressure evaluation in liquids) techniques—are able to quantitatively determine hydrogen content directly in the melt. In testing, both showed outstanding agreement with regard to accuracy and reproducibility. Two analytical methods were also studied—vacuum solid extraction and carrier fusion extraction. Both the direct and analytical methods yielded satisfactory agreement among the results. Also studied was an indication method, reduced-pressure testing, which is a quick and simple method suitable for the qualitatively evaluating hydrogen content. Here, however, the relationship between the density index and the hydrogen content of the melt is influenced by numerous factors.