Normal/low-temperature chemical conversion solution for 35CrMnSi steel and preparing method thereof

The invention discloses a normal/low-temperature chemical conversion solution for 35CrMnSi steel and a preparing method thereof. The conversion solution consists of the following components in percents by weight: 10-30% of nitric acid, 5-15% of phosphoric acid, 15-25% of zinc oxide, 1-5% of iron powder, 5-10% of a compound accelerant and the balance of water, wherein the compound accelerant is prepared from citric acid and chlorate. The preparing method comprises the following steps: (1), dissolving the zinc oxide in the nitric acid and the phosphoric acid; (2), then, adding the compound accelerant, and after fully dissolving, adding the water; and (3), adding the iron powder into a solution obtained in step (2), taking out the iron powder after curing, and regulating the pH value to 2.0 to 3.0. The normal/low-temperature chemical conversion solution for 35CrMnSi steel does not contain toxic components, the use method is simple and is easy to operate, energy consumption and production cost are low, one layer of even and dense conversion film consisting of 2-5mum flaky zinc phosphate crystals can be formed on the surface of a base body, and the corrosion resistance is great.