The commonly used complexing agents for passivating agents are citrate and acetate in a mixing ratio of: 28 parts of sodium citrate and 1220 parts of acetic acid. The mixing ratio of citrate and sodium acetate in the passivation agent is 28 parts of sodium citrate and 1220 parts of acetic acid. 1,220 parts of acetic acid, 28 parts of sodium citrate, 310 parts of cobalt nitrate, 615 parts of sodium phosphate, 412 parts of phosphoric acid, 16 parts of potassium ferricyanide, 49 parts of sodium molybdate, 515 parts of water-soluble persulfate, and 3,001,000 parts of water.