Film, film forming method, and surface-coated material

1. A film forming method comprising repeatedly alternately applying a first potential and a second potential to a Ni material in a state where the Ni material is immersed in an alkaline solution, such that a film that contains Ni 2 O 3 H as a main component is formed on a surface of the Ni material, wherein:

the first potential is a potential at which Ni turns tetravalent in a Ni—H 2 O system;

the second potential is a potential at which Ni turns divalent in the Ni—H 2 O system; and

the alkaline solution comprises at least one of NaOH and LiOH.

2. The film forming method according to claim 1 , wherein the alkaline solution has a temperature of 40° C. to 90° C. and a pH of 10 or higher.