| 摘要 |
PROBLEM TO BE SOLVED: To prevent charging efficiency in the initial stage from being deteriorated, by specifying a pH value in the treatment of hydrogen storage alloy in acidic solution. SOLUTION: Hydrogen storage alloy is immersed into acidic solution whose initial pH value is 2 or less. Therefore, a layer of oxide on the alloy surface is removed, rare earth elements of Mn, Al having the high ionization tendency in alloy are dissolved, a number of active parts having many Ni compounds appear on the front surface side, and dissolved ion is deposit on the surface of alloy. When pH of acidic solution reaches the specified value in the range of 3 to 5, alloy is taken out and washed in water, and ion deposited on the surface is removed. When alloy is immersed into acidic solution having a pH value equal to a predetermined value, oxide remaining on the alloy front surface is dissolved, a number of active parts having many Ni compounds appear on the alloy front surface. As a result, hydrogen gas is sufficiently absorbed to alloy from the initial stage, and charging efficiency is improved. |
