Hydration of commercially-pure Al powder in distilled water at 25 to 100℃ has been investigated. Bayerite Al(OH)3 product layers formed on Al at 25-40℃ were porous, so the hydration rate, although very slow at 25℃, increased rapidly with increasing temperature from 25 to 45℃. On further increasing temperature from 45 to 95℃, initial hydration rate increased, but changed little over long hydration periods due to formation of denser and more continuous product layers. At 100℃, because of rapid water evaporation, hydration product layers (composed of Al(OH)3 and a small amount of boemite AlO(OH)) became detached from the Al surfaces, so offering less production, so that the hydration rate of Al increased again.

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