Research On Analytical Apparatus For Detecting The Amount Of Chromium

As it has the advantages of high hardness, good abrasiveness and graceful appearance, chrome plating is applied in hardware embellishment, domestic electric appliance and machine manufacture far and wide. But if the depth of chrome plating layer is less than 20μm, the advantages mentioned above can not be acquired. On the other hand, if it is too thick, the prime cost will be too high. In such a fashion, that the detecting of the amount of chrome plating is very important.There are several methods to detect the amount of chrome plating, such as spectrograph method, capacity method, X ray fluorescence method and coulomb method. Among them, the coulomb method which is based on Faraday'electrolysis law is fast, accurate and repeatable, and has been defined as arbitrage test in a relative standard. But the traditional coulomb method has the defect of being unable to ascertain the time of electrolytic disassociation to an inch.The paper brings forward a method of differential electric potential, which is the improvement to the traditional coulomb method. The method of differential electric potential makes electrolysis potential of chrome plating layer and the alloy layer of chrome and iron differentiate against time utilizing differential circuit, and therefore transforms the change of electrolysis potential to a cuspate pulse wave. In this way, an accurate time of electrolytic disassociation of chrome plating layer and the alloy layer of chrome and iron can be acquired and the depth of chrome plating layer can be figured out. The new method surmounts the defect of the traditional one, reduces the measuring error and improves the measuring precision.The apparatus utilizes the following new techniques in the hardware design: differential electric potential stratification method, numerical control and residual current power source, high-precision clocking and optimum differential capacitance select, which advances the degree of accuracy and automation. In the software design, the sampling peak is optimized and the error of calculative result is corrected. The measuring precision of the apparatus is lower than 1%, resolution is 0.001g/m2, repeatability is superior to 0.5% and the technical indicator and automation extent achieve and even exceed the international level of the same apparatus. The successful development of this apparatus fills the vacancy of dedicated detecting apparatus of the amount of chrome plating in China.