Study on characterization technology of metal phosphating layer

In this paper, the aluminum metal thin layer protective layer with a micron-sized was pre-evaporated on the surface of the phosphating layer sample by vacuum thermal evaporation. The presence of a metal aluminum layer can effectively prevent the diffusion between the inlay and the phosphate layer during sample preparation. Moreover, due to the bright color of the metal aluminum layer under the optical microscope, a bright strip can be formed on the phosphating layer, which can accurately locate the end point of the thickness measurement under the metallographic microscope and improve the accuracy of the thickness measurement. It can be shown that the thickness of the surface phosphating layer is about 8.047μm. And the result meets the designed technical index of phosphating layer thickness (≤10μm). Furthermore, the test characterization method can also provide indirect evidence for the uniformity of the phosphating layer.