Gravure Plate Plating Process Optimization (I)

After the gravure platemaking technology was introduced from abroad, electroplating has always used the original electroplating process, that is, pre-plated sulphate dark nickel/sulphate bright hard copper/hard chrome three kinds of coating, this combination, although can get good The combination of strength and appearance, but the anticorrosion performance of the platen roller has not been very good. There is no problem in the case of single use of the platen roller. However, after the Plate is used for a period of time, deinking, sweeping, and chrome removal will occur. In order to improve the service life of the platen, it is necessary to find a method that does not need to fundamentally change the existing technological process, and does not need to add equipment. Without increasing the investment, the service life of the plate cylinder will be greatly improved. It requires the technologist to optimize the electroplating process in the gravure process.

Problems with traditional plating processes

In gravure platemaking, the traditional electroplating process is pre-plated sulphate dark nickel/sulphate plated hard copper/hard chrome. The combination of these three coatings has been used until now. At the beginning, there were fewer plate-making factories. In the case of “supply far less than demand,” plate-making plants and customers would not consider too much about the anticorrosive properties of the plate cylinders. However, in the situation where the plate-making plants are still standing and competition is fierce, The service life of the platen roller has also become a selling point of the merchants. Many plate-making factories have promised the lifetime warranty of the platen roller. The anticorrosion of the platen roller has become the focus issue of the plate-making factory.

Conventional electroplating process can only improve the corrosion resistance of the plate cylinder by limiting the thickness of the chromium layer and improving the quality of the chromium layer to a certain extent (such as increasing the toughness of the coating, increasing the amount of cracks, and reducing the penetration porosity). In the case of a certain plating quality, its corrosion resistance is almost proportional to the thickness, but the internal stress of the chromium layer itself is too large, too thick coating is also easy to explode chrome, which will reduce the production efficiency and increase the energy consumption. To take into account the problem of over-thick chromium layer loss of electric engraving dots. In other words, it is difficult to further improve the anti-corrosion performance of the platen at present.

The traditional corrosion resistance of the electroplating process is not good due to the following two aspects.

(1) The chrome plating layer has too many penetrating cracks and cannot effectively protect the contact between the copper matrix and the oxide, and the copper layer itself has poor corrosion resistance. Once the copper layer is corroded by contact with the oxide, it will be due to Volume expansion causes the flatness of the chromium layer to decrease, deinking, knife lines, and even the chrome layer to fall off.

(2) Although the electrode potential of metallic chromium is lower than that of copper, the chromium layer is easily passivated in air, making its own potential higher than that of copper. In the presence of electrolytes, copper is used as the anode and chromium is used. The galvanic reaction of the cathode causes the copper layer to corrode, causing deinking or chrome bleed, especially in high temperature and humidity conditions.

New process flow

With the development of the electroplating industry, there are the following types of plating that have always dominated the field of anticorrosion plating.

(1) Copper cyanide/bright nickel/decorative chromium or hard chromium.
(2) Dark nickel/acid bright copper/bright nickel/decorative chromium or hard chromium
(3) Semi-bright dark nickel/bright nickel/decorative or hard chromium.
(4) Dark nickel/high nickel/brilliant nickel/decorative or hard chromium.

The above-mentioned several kinds of anti-corrosion electroplating process nickel plating accounted for a more important position, because the nickel plating layer crystal fine, high coating stability, good anti-corrosion properties. In addition, although the nickel layer has a high voidage, the corrosion potential of the nickel layer is reduced due to the difference in the electrode potential of the multi-layer coating when a small corrosion cell is formed, which effectively slows the progress of corrosion and improves the corrosion resistance thereof. .

Similarly, the anti-corrosion electroplating process that has been more matured has been used in the plate making industry to improve the anti-corrosion performance of the platen. The better electroplating process is: dark nickel/sulphate bright hard copper/sulfamate nickel/hard chromium, amino Nickel sulphonate thickness need not be too thick, 3-5 μm can be. However, taking into account the cost of the nickel sulfamate process, the cost of new equipment, and the current resource utilization of the current platemaking company (the new plate mill may consider using the above process), the process can be changed to: Sulfate semi-bright nickel/sulphate Copper/sulphate semi-bright nickel/hard chrome. The properties and appearance of the semi-bright nickel sulphate coating do not require the addition of new equipment, although there is no nickel sulphamate coating performance, the process flow does not change much, and there is no need for excessive cost, and more importantly, this process Anti-corrosion performance in theory is also more than doubled than that of the existing electroplating process, which has a very high practical value for relieving the current plate-making company with a large number of external reflow plates every month. Reducing costs and improving the company’s overall competitiveness also have a very positive effect.

(to be continued)