Environment-friendly passivating agent for performing treatment before color coating and preparation method thereof

The invention discloses an environment-friendly passivating agent for performing treatment before color coating and a preparation method thereof. The environment-friendly passivating agent comprises 1.0-10.0 percent of water-soluble epoxy resin, 1.0-10.0 percent of organo-silicone, 0.5-5.0 percent of soluble molybdate, 2.0-10.0 percent of nanometer silica sol, 0.5-5.0 percent of soluble tungstate and the balance of water. The preparation method comprises the following steps of: hydrolyzing organo-silicone with ethanol of which the concentration is 20-60 percent; uniformly mixing the hydrolyzed organo-silicone with water-soluble epoxy resin, and reacting at the temperature of 75-82 DEG C for 20-40 minutes to form a solution A; dissolving molybdate and tungstate into deionized water respectively, stirring uniformly, adding nanometer silica sol of which the granularity is 10-20 nanometers, and adding while stirring to form a solution B; and fully mixing and uniformly stirring the solution A and the solution B, and adjusting the pH value of a mixed solution to 6.5-7.5 with nitric acid or ammonia water.