Method for analyzing cadmium chloride in acid cyanide-free cadmium plating solution

Abstract

The invention discloses a method for analyzing cadmium chloride in an acid cyanide-free cadmium plating solution. The method includes the steps that a coordination agent in the acid cyanide-free cadmium plating solution is oxidized with ammonium persulfate under the strong acid condition so that cadmium ions can be released from coordination ions; iron ions are masked with ascorbic acid and aluminum ions are masked with triethanolamine under the condition that pH ranges from 9.5 to 10, an excess EDTA standard solution is added to coordinate with cadmium ions, eriochrome black T serves as an indicator, EDTA is subjected to back titration with a zinc sulfate standard solution, and the mass concentration of cadmium chloride in the plating solution is calculated with a minusing method. According to the method, in the testing process, sulfuric acid is added into the tested solution to make the tested solution have strong acidity, and then the coordination agent is completely oxidized with ammonium persulfate under the heating condition, so that interference of the coordination agent with cadmium chloride determination is eliminated. The method is accurate in determination result and superior to an existing method.

Description

technical field [0001] The invention relates to an analysis method for cadmium chloride in an acidic cyanide-free cadmium plating solution. Background technique [0002] Due to the excellent corrosion resistance and softness of cadmium plating, aerospace parts are still prepared with cadmium plating process for protective layer. The traditional cyanide cadmium plating process uses sodium cyanide as a complexing agent, and cyanide is one of the pollutants strictly prohibited by the state. In accordance with the requirements of the National Development and Reform Commission's "Industrial Structure Adjustment Catalog (2011 Revised Edition)", some aerospace companies are replacing traditional cyanide cadmium plating with acidic cyanide-free cadmium plating. [0003] The analysis of cadmium chloride in acidic cyanide-free cadmium plating solution currently adopts EDTA volumetric method [1] , the method uses ammonium persulfate to oxidize the complexing agent in the plating solu...

AI Technical Summary

Problems solved by technology

[0005] The present invention proposes an analysis method for cadmium chloride in an acidic cyanide-free cadmium plating solution, using ammonium persulfate to destroy complexing agents such as nitrilotriacetic acid in the plating solution under strong acidity and heating conditions, and adding excessive EDTA standard solution Coordinate cadmium ions, back-titrate EDTA with zinc sulfate standard solution, and calculate the mass concentration of cadmium chloride in the plating solution by subtraction method, which solves the problems of low measurement results of existing methods and insufficient sensitivity or even inability to change color at the titration end point