To improve the protection against corrosion to a positive electrode active material to raise the life performance by constituting a battery jar from an iron or iron alloy containing a specified quantity of carbon, and chromizing the surface of the iron or iron alloy a specified number of times.

A battery jar is formed of an iron or iron alloy containing 0.1% or less of carbon, and the surface of the iron or iron alloy is chromized 1-3 times. When the carbon content of the iron or iron alloy exceeds 0.1%, a chromium carbide such as Cr23C6 or Cr7C3 is formed on the surface of the base metal in chromizing. This chromium carbide prevents the diffusion of chromium to the base metal and, further, sufficient corrosion resistance cannot be provided since this carbide is easy to decompose. Since a Cr-Fe alloy layer with sufficient thickness and concentration cannot be formed by one chromizing, the temperature is lowered after the first work, and then again raised to perform the second chromizing or the third chromizing in the same process.