Determination of Ni~(2+) content in Zn-Ni alloy electroplating solution with carmine red fading spectrophotometry

In the buffer solution of hexamethyle netetramine-hydrochloric acid of pH=5.4 with water bath of (100 ℃,) carmine red can be oxidized to fade by hydrogen peroxide, in which Ni~(2+) is used as catalyst, and thereby carmine red fading spetrophotometry was promoted to measure the Ni~(2+) content in Zn-Ni alloy electroplating solution. The relevant experimental conditions were obtained and the suitable wavelength was 518 nm. The influences of the apparent activation energy of Ni~(2+) catalytic reaction and the impurity ions in the solution on the testing results were discussed. The Ni~(2+) content in the alkaline Zn-Ni alloy electroplating solution of one electroplating factory was tested. The results show that this method is easy and highly accurate, and can meet the demand of fast measurement in production.