Analysis And Monitoring Of Substitution Chromium Tungsten Alloy Electroplate Baths

At the base of understanding the actuality of chromium alternative process was investigated, the analytical method of determining different substance in electroplating bath has been studied, the disposal effects of different methods and applied object were analyzed in contrast, and the monitoring analytical methods of different substance in chromium alternative were confirmed.The paper established a series of Ultraviolet Absorption Spectrometry ways to analysis the different substances in Ni-W-P alloy electroplating bath. The influences of other components in the electroplating bath on determination of each determination methods were discussed.1. Tungsten (VI)-PF (9-Phenyl-2,3,7-trihydroxy-6-fluorine)-CTMAB (cetyltrimethy- lammonium bromide) Spectrometry analysis ways:the absorption spectrum character of Tungsten (â…¥)-PF (9-Phenyl-2,3,7-trihydroxy-6-fluorine)-CT-MAB (cetyltrimethyl-ammonium bromide) ternary complex was studied by using spectrophotometer method in the hydrochloric medium. The influences of other components on alloy electroplating solution such as citric acid as the complexing agent,sodium hypophosphite as reductant and other coexistence components on determination of tungsten content were discussed. The results showed that, while the concentration of Ni2+,Fe3+ and citric acid was 3 times,3 times and 200 times of the concentration of W6+ respectively, the affection on determination of tungsten content can be ignored, and the concentration of sodium hypophosphite had no effect on the determination of tungsten content. The method was rapid and accurate, and can be used to determine the tungsten content in the alloy electroplating solution.2. Fe3+ coloring method of citric acid:in this experiment, the color reaction of iron (â…¢) in the hydrochloric medium with citric acid and spectrophotometry were used to determine the content of citric acid. The influences of other components on alloy electroplating solution such as sodium tungstate as the main salt, sodium hypophosphite as reluctant and other coexistence components on determination of citric acid content were discussed. The results showed that while the concentration of Ni2+,Fe3+,Fe2+ and sodium hypophosphite was not more than 0.5 times of the concentration of citric acid, the affection on determination of citric acid content can be ignored. Sodium tungstate has some impact on determination the content of citric acid and the impact can be deducted by spectrophotometric analysis in order to accurately measure the content of citric acid in Ni-W-P alloy plating solution. The method was rapid and accurate, and can be used to determine the citric acid content in the alloy electroplating solution.3. Discoloration spectrometry analysis ways of citric acid:in the HAc-NH4Ac medium ferric ions react with citric acid to form violet-red complex. The color of the complex will be discolored to orange red by adding a definite amount of standard citric acid. The decease of absorbance is proportion to the content of citric acid at 490nm and the linear range of citric acid is 0.2" 50mg/L.4. KMnO4 oxidation spectrometry analysis ways of citric acid:citric acid under the action of permanganate can turn to acetone dicarboxylic acid. We can determination the content of citric acid by spectrometry. In acid condition, the influence of sodium tungstate can be eliminated. Because of potassium permanganate has the oxidation function, this method only used in the alloy electroplating solution which not contains reducing agent.In summary, methods established in our research can be applied to determination different substances in electroplating bath effectively. It is convenient in practice activities and can be spread among factories.