Intaglio printing plate electroplating process - Chrome plating: Process conditions!
Release Time:
Dec 15,2017
Chrome plating process conditions
1. Selection of chrome plating anodes
The anode in the plating tank is best made of titanium mesh coated with platinum, which has good adhesion of the chrome layer and is not easy to fall off.
It is recommended to use products from Maituo Company.German sintered titanium-based platinum-coated anodes ↓
Performance advantages ↓
German sintered anodes have excellent electrochemical performance, low oxygen absorption potential, which helps to reduce production energy consumption and lower anode operating temperature; excellent oxidation capability,ensuring the balance of trivalent chromium content in the plating solution and the stability of the solution composition.Due to the special surface structure, it ensures that the volume of bubbles generated by the anode during production is relatively large, resulting in less carry-out of the plating solution and reducing the consumption of raw materials such as chromium anhydride.；2. Chrome plating temperature
The chrome plating temperature should be controlled at 50-60°C, with the best range being 52-55°C. A higher chrome plating temperature results in a softer chrome layer; for every 1°C decrease in temperature, the hardness increases by 60HV. Due to hydrogen evolution, the pH value in the cathode area rises, leading to the following conversion:
Cr
2O72++HO →2CrOO42-+2H+CrO
+8H2-+2H+6e →Cr+4HCrO3. Adoption of standardized chrome plating processO7
Some plating companies have standardized the chrome plating process, using a Japanese-style full immersion method at 50°C and 40A/dm.
This can achieve a chrome layer hardness of 820HV. Practice has proven that this process condition is mature; as long as the solution is stable, it is a good choice.O4. Use of hard chrome additives
Currently, many domestic plating manufacturers are adding an appropriate amount of chrome plating additives to hard chrome plating solutions.
It is reported that adding a rare earth additive to low-chromium plating solutions has played a significant role in solving the issues of low deposition speed of chromium in chromic acid plating, increasing the current efficiency of ordinary high-chromium plating solutions from 6%-15% to 20%-31%, increasing deposition speed by 60%-110%, and improving hardness by 30%-60%, making it suitable for wear-resistant hard chrome plating. However, there are also issues with stability and reliability in production. Therefore, when selecting additives, the principles of advancement, stability, and economy should be followed.Currently, many plating companies choose Maituo Company's German hard chrome plating process VOP-Cr873, which has shown good results. The German hard chrome additives are divided into three types: opening agents, transfer agents, and replenishing agents. Generally, replenishing agents are used, added directly to the plating tank in a certain proportion to maintain production. Practice has proven that a ratio of 1 kilogram of chromium anhydride with 75ml of replenishing agent can improve current efficiency (cathodic current efficiency of 20%-27%), accelerate deposition speed (generally when DK=50-80A/dm2, the single-sided deposition speed can reach 50-100μm/s), enhance the uniform plating ability of the solution (under normal circumstances, the dispersion ability of German hard chrome additives is about 1.5 times that of ordinary electroplating solutions) and the hardness of the plating layer (hardness ≥ HV850), and the wear resistance is also improved by about 20% compared to ordinary processes, with good adhesion of the plating layer. The special formula reduces tip discharge, making the sharp parts of the plated items smooth, greatly reducing the risk of wire drawing on gravure plates, and exhibiting excellent micro-cracking, more than similar products, enhancing the corrosion resistance of the chrome layer.5. Master the area ratio of the copper roller immersion area to the anode area, that is, the area of the copper roller immersed in the chrome plating solution to the area of the titanium mesh, which should be at least 1:2 to 2:3.6. The rotation speed of the plate roller should be adjusted according to the diameter of the plate roller.7. Chrome plating time: The traditional chrome plating time is 40 minutes, while hard chrome plating takes 25 minutes.
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