Abstract
The influence of moisture on the reliability of the determination of hydrogen in aluminium by the N2 carrier fusion method was studied. It was found that it is necessary to keep the water vapor in the hydrogen-extraction area at under 10 mg/m3 in order to lower the surface hydrogen to less than 0.01 ppm (the instrumental detection limit). The surface waters on an aluminium sample was 'adsorbed' water liberated by heating at a temperatures lower than 473 K, and 'combined' water by heating above 573 K, both of which produced surface hydrogen. The combined water produced surface water much more than the adsorbed one. Essentially, although it was difficult to eliminate the influence of surface hydrogen on the determination of hydrogen, the surface water could be reduced to 1 mg/m2 or below by machining the sample in the cylindrical form under an atmosphere (3000 mg H2 0/m3) with a stream of nitrogen. As a result, the surface hydrogen could be decreased to 0.01 ppm or less. In real analyses, however, surface hydrogen could also be achieved to 0.01 ppm by machining the sample very carefully with an ethanol lubricant at room atmosphere. An analysis of commercial high-purity aluminium ( JIS 1N99), showed an average concentration of 0.092 ppm hydrogen and a relative standard deviation of 6.0% (n =30).
