| 摘要 |
PROBLEM TO BE SOLVED: To raise the capacitance per unit area by a first pretreating of dipping in a weak alkaline water soln., a second pretreating of soaking in an acid water soln. and an etching process. SOLUTION: For pretreating an Al foil, a first pretreating of soaking in a weak alkaline water soln. and a second pretreating of soaking in an acid water soln. for forming a film on the Al foil surface are made, followed by an etching process. The weak alkaline water soln. used in the first pretreating uses a kind of water soln. selected among carbonate water soln. Na, Na borate, monoethanolamine, diethanolamine, and triethanolamine or a mixed water soln. thereof and is set with a pH of 7.8-10.8 and a temp. of 20-60 deg.C.
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