After two weeks of wear resistance testing of the chrome plating layer at Factory 2, relevant data was obtained mainly by orthogonally combining the temperature and current density used in the chrome plating process. The actual testing steps and interim conclusions are summarized as follows.

Testing Steps:

1.Preparation: Factory 2 prepared two printing rollers, with specifications of 540*1150and 450*1100(circumference*length/mm). The rollers were first copper plated, and then engraved with four different electric engraving processes of dark tone mesh patterns (size 150mm*150mm). Before testing, the initial mesh values of various patterns were measured on the engraving machine and recorded in a table.

2.Chrome Plating: The planned chrome plating thickness is 6-7um, and the required time is calculated based on the current density used in each experiment. To eliminate the influence of chrome plating thickness on the experiment, the two rollers were plated in two batches. Each time was conducted in Factory 2's chrome tank #2, and the composition of the plating solution in tank #2 before the experiment was as follows: Chromium anhydride: 260g/L, Trivalent Cr: 2.4g/L, Sulfuric acid: 2.5g/L.3.Pre-polishing Measurement: After the first three chrome platings were completed, the mesh values measured on the engraving machine showed almost no change compared to before chrome plating, concluding that chrome plating has no effect on mesh values. Therefore, the step of measuring mesh values before polishing was omitted in subsequent experiments, using the data from the first three times. The data to be measured before polishing includes coating thickness and coating hardness.

4.Polishing: Each polishing was performed on the same chrome surface polishing machine, with all set parameters being the same as follows: Speed: 1.8m/s

, trolley speed 20mm/revolution, grinding head vibration frequency: 40Hz, sandpaper: 40μ, polishing force for 12 back-and-forth passes.5.Mesh Value Measurement: Each measurement used the same engraving machine to eliminate testing errors, measuring three times at the same process and taking the average value.

6.Dissolution: Factory 2 uses hydrochloric acid for chrome dissolution, with each dissolution taking about 20

minutes to half an hour, and after dissolution, the experiment is repeated starting from step two. After multiple dissolution tests of mesh values, it was found that dissolution has little effect on mesh values.7.Data Statistics: The measured data is recorded in a table, subtracting the post-polishing mesh value from the pre-polishing mesh value and calculating the average.

Experimental Conclusion:Among the various combinations of current density and temperature used in the tests, the best wear resistance was found at 50A/dm

 2

1.54^{℃, followed by 70A/dm}56℃, 60A/dm56℃. In other words, at 54-56℃, the wear resistance of the coating is generally good. When the temperature rises to 60℃, the wear resistance slightly decreases. When the temperature drops to 52℃, the decrease in wear resistance is more significant. The effect of current density on the wear resistance of the coating is not very large.The data shows that there is a certain correlation between coating thickness and wear resistance. The relationship between coating hardness and wear resistance is not directly proportional. It should also be noted that the hardness of the coating actually increased after polishing compared to before polishing.^{℃, followed by 70A/dm}Error Analysis:^{℃, followed by 70A/dm}During chrome plating, due to the different diameters of the plates, the immersion areas are also different, but the calculation can only be based on half immersion, so there is a certain error in the calculation of current density.

2.Dongyun Chemical Technology Department

2010-10-3

镀铬时由于版直径不同，浸入面积也不同，但计算时只能按半浸入，所以对电流密度的计算存在一定误差。

东运化工技术部

2010-10-3