Analysis method for iron impurities in trivalent chromium passivation solution

The invention discloses an analysis method for iron impurities in a trivalent chromium passivation solution. The analysis method comprises the steps that firstly, the solution is prepared; secondly, under the condition that a pH value is equal to 10, the absorbancy of a standard iron solution is tested, and a standard curve of the corresponding relation between the mass concentration and the absorbancy of iron is drawn; thirdly, the trivalent chromium passivation solution is absorbed into a volumetric flask, a sodium citrate solution is added, an ammonia-ammonium chloride buffered solution is further added, wherein the pH value of the ammonia-ammonium chloride buffered solution is equal to 10, water is added, and attenuation is carried out until the scale is reached, even shaking is carried out, and a reagent serves as a blank solution; fourthly, the trivalent chromium passivation solution is absorbed into the volumetric flask, the sodium citrate solution is added, a ferrotitanium reagent is further added, the ammonia-ammonium chloride buffered solution is further added, wherein the pH value of the ammonia-ammonium chloride buffered solution is equal to 10, even shaking is carried out, and the reagent serves as a to-be-tested solution; fifthly, the blank solution serves as the reference, the absorbancy of the to-be-tested solution is tested at the 500 nm portion in the wave length; sixthly, the mass concentration of the iron impurities is checked on the standard curve. According to the method, the content of the iron impurities in the trivalent chromium passivation solution can be tested rapidly and accurately.