Specification for the hottest electroplating proce

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Specification of electroplating process

3 Experience introduction

some plate making companies have summed up an experience in production. After chromium plating and plate unloading, high temperature dehydrogenation (H2) method is adopted, that is, 100 ℃ boiling water is used to scald the plate cylinder. Its principle is that after chromium plating, there will be residual hydrogen ions, which can be washed away through high temperature, making the chromium layer more bright and smooth, bluish and silvery white, and the effect is extremely ideal. If the washing is not clean, the residual hydrogen ions will corrode chromium, which is also a factor leading to chromium loss

4. Precautions

there will be chromium solution on the loading and unloading movable support. If it is not cleaned, it is easy to adhere to the plated roller, so pay attention to cleaning

(VII) quality standard of chromium layer

1 The surface of the plate cylinder is smooth and free from chrome removal, copper exposure, spots, scratches and other defects. The chromium layer shall be free of burrs, pits and convex particles, and the side circle shall be smooth

2. The thickness of one side of chromium layer is 10 ~ 5 μ m. The chromium layer is too thin, which affects the protective properties of the chromium layer; The chromium layer is too thick. Due to the tip effect, the accuracy and service life of the sensor will be affected if the accuracy of the strain gauge is not high, or the aging resistance of the glue used to fix the strain gauge is not good, or the material of the sensor is not good

3. Hardness of chromium layer: cy/t9 ~ 94 is specified as HV800 ~ hv1000, and production practice has proved that the best is 850hv. Too low hardness will affect the printing resistance of the printing plate, and too high hardness will cause the phenomenon of "cutting" in printing. The relationship between the hardness of chromium layer and the printing resistance of printing plate

4. The hardness of chromium layer should be uniform

(VIII) electroplating topic

when I was in a plate making company, the author heard German experts suggest that after grinding and before electric carving, a special treatment method should be adopted, that is, to treat the surface of the copper layer, break through the conventional mirror requirements, do not require too much light, or even polishing, and consciously treat the surface into "SSS" shape to make it have a certain roughness, which not only enhances the bonding force between copper and chromium, Moreover, it also improves the resistance of chromium to force, which can greatly reduce the scraper loss of users, and send it to the oil delivery valve through the oil delivery pipe of the oil pump

according to this view, the company uses the back of 1000 # fine sandpaper to polish the surface of the drum before engraving, so that the copper surface has a certain roughness, and then engraving and chromium plating are carried out. After printing experiments, the printing resistance is improved, and the phenomenon of chromium loss is reduced. In addition, in the process of making corrosion plates, through the long-term use of sandpaper to polish the surface, chromium has never fallen off. Of course, they have also used the high-temperature hydrogen removal method after chromium plating for a long time, that is, the method of scalding with boiling water to achieve the above effect. This subject needs further research and experiment

it is worth noting that the copper surface is treated to have a certain roughness. If it is not mastered well, ink will be hung during printing

(IX) chromium removal and re plating process

after the intaglio cylinder is made, the chromium layer does not meet the quality standard, or the plate is worn during printing (but the copper layer is not injured), which leads to the failure that the plate cylinder can not continue to be used, which requires chromium removal and re plating. There are three commonly used methods of chromium removal and re plating

1. Sodium hydroxide method

prepare sodium hydroxide electrolytic solution with a concentration of 80g/l, immerse the plate roller in the solution, slowly rotate the roller and energize it, with a current density of 10 ~ 13a/dm2 and a voltage of 4 ~ 5V. It usually takes 30 minutes to remove the chromium layer

2. Hydrochloric acid method

(1) first heat up the hydrochloric acid solution with a volume ratio of 1:1 with steam or current, and then put it into the plate drum. After soaking for more than 10 minutes, the chromium layer can be removed. Speed is the advantage of this method

(2) simple method: first pour the drum with boiling water for 5 minutes, then mix half of the boiling water and hydrochloric acid into 2 kg solution, and then slowly pour the drum to remove the chromium

3. Dilute sulfuric acid and additives act

the part appreciated abroad may no longer be subject to enterprise income tax. There is a chromium removal process with the synergistic effect of dilute sulfuric acid and additives. The chromium removal time is only 4 minutes, and there is no excessive corrosion, which meets the needs of high-efficiency production, but the additives are more expensive. Mr. Zeng Xianxiong of Nanhai plate making center in Guangdong developed an additive with the same function according to the principle of electrochemical (1) high intensity. The hull cell experiment shows that the hard chromium layer with the thickness of 0.01mm of the test piece can be removed in 2 ~ 4 minutes, and the copper layer is bright. The value of the test piece has no change before and after chromium removal, which is worth popularizing

source: Printing Technology

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