Metal Finishing Guide Book


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Bath Type Analytical Method KAu(CN)2 AA, ICP, gravimetric KCN Alkaline gold Parameters Titration, ISE, IC, colorimetry K2CO3 or KOH Titration Phosphates/citrates Citric acid NA AA, ICP pH Electrode KAu(CN)2 AA, ICP, gravimetric KH2PO4 NA pH Electrode Grain refiners: Tl, As AA, ICP, polarography NaAuCl4 AA, ICP, gravimetric Na2SO3 NA Na2S2O3 NA Na2HPO4 NA pH Non-cyanide gold AA, ICP, gravimetric Cobalt or nickel Neutral gold (additive free) Electrode KAu(CN)2 Acid cyanide gold NA pH pH electrode NA = not analyzed. Table 4: Analysis of Gold Baths After additions to the tank and adequate mixing, an analysis should be performed again to check desired parameters. Normally, well-established plating shops have reasonably good laboratories and are well equipped to keep track of their chemistries. Some job shops depend on analytical support from chemical bath suppliers, which are usually away from site, and they have key parameters analyzed once or twice a month. The drawback of off-site analysis is that bath components cannot be adjusted in a timely manner. Reagent-grade standardized solutions should be procured from a reliable supply house. A well-trained chemist may prepare his own solutions and standardize versus primary standards. The initial receipt date and expiration date of these solutions should be recorded. Deionized or distilled water should used in the analysis. Common standard solutions such as HCl, H2SO4, NaOH, Na2SO3, AgNO3, I2, K2Cr2O7, KMnO4, and KCSN are available in 0.1-N concentrations. 461

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