Film-forming solution for forming electrochemical oxide film on surface of steel, application method thereof and film formed therefrom

The invention discloses a film-forming solution for forming an electrochemical oxide film on the surface of steel, an application method thereof and a film formed therefrom. The film-forming solution comprises the following components: manganese dihydrogen phosphate, fluorosilicate and nitrate used as main salts, ascorbic acid and dodecyl sulfonate used as additives and phosphoric acid used as a pH regulator. The invention is characterized in that the film-forming solution comprises the following components: 50-100g/l of manganese dihydrogen phosphate, 5-20g/l of fluoroborate, 50-80g/l of nitrate, 1-10g/l of ascorbic acid, 0.5-1g/l of dodecyl sulfonate; the pH value is regulated with the phosphoric acid to 1-3; a plain steel plate, titanium plate or graphite plate is used as a cathode material; and the process conditions are as follows: the temperature is 10-30 DEG C, the current density is 0.1-1.5A/dm , the voltage is 50-200V, and the oxidation time is 30-60 minutes. According to the invention, an electroche