Effects of moisture and dissolved oxygen in methanol and ethanol solutions containing hydrochloric acid on hydrogen absorption and desorption behaviors of Ni–Ti superelastic alloy

The effects of moisture (H2O concentration) and dissolved oxygen in methanol and ethanol solutions containing 0.1% hydrochloric acid (HCl) on hydrogen absorption and desorption behaviors of the Ni–Ti superelastic alloy have been examined by hydrogen thermal desorption analysis. In the methanol solution, the amount of absorbed hydrogen decreases with increasing H2O concentration. For 5% H2O, the thermal desorption peak of hydrogen gradually shifts from 400 to 250 °C with immersion time. When the H2O concentration is higher than 10%, the hydrogen absorption is not observed. Under a deaerated condition, significant dissolution of the specimen due to corrosion is observed; however, the increment in the amount of desorbed hydrogen is not observed. In the ethanol solution, the critical H2O concentration for hydrogen absorption is approximately 0.8%. For 2% H2O, the hydrogen absorption is not exhibited, although slight corrosion is observed. The amount of absorbed hydrogen under the deaerated condition is ten times more than that under the aerated condition. The dissolved oxygen varies the hydrogen desorption behavior.