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What to pay attention to before plating zinc alloy products
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How should zinc alloy products be treated before plating? In the electroplating process of zinc alloy products (qualified components, qualified die casting process, and blank defects), there are problems such as foaming, low index of adhesion, and etch points. Zinc alloy substrate is different from copper substrate in deplating, re-polishing, and back plating. At present, there is no ideal deplating agent to remove copper and nickel on zinc base without corroding the substrate, and the cost of re-plating is high. The pass rate is low, and zinc alloy products may cause waste due to blistering, poor bonding force and etched spots. Therefore, in order to obtain a good coating, pre-plating and pre-plating are the key1. Polishing: The surface should first be ground to the surface burrs, parting lines, flashing surface and other surface defects. There are three methods: cloth wheel polishing on the cloth wheel or continuous cloth tape adhesion granularity is 0.045 ~ 0 The .069 mm abrasive is supplemented with butter paste. The new sticky material should be inverted before use. When the cloth wheel is used to polish the surface of the part, use a speed of 1 100~1400 m/min. When grinding, do not dry it. The pressure of polishing should not be too large: this can prevent Partial overheating of parts and avoiding excessive grinding:
2. Rolling: Rolling and polishing was carried out in a drum equipped with abrasive (granite ceramic) and rolling liquid (5% 38 detergent, 3% wax removal water). The mass ratio of abrasive to part is approximately 2.25:1.00. The rotation speed of the drum should not be high to prevent damage to the surface of the part, usually 5 r / min, and the time is 1.5 ~ 2.0 h.
3, polishing: polishing can make the parts get mechanical leveling and bright. Polishing should be carried out with a whole cloth wheel. After polishing with a butter paste and then polishing it with white grease, it should be used sparingly.
Because the polishing paste will cause the polishing wax to stick to the concave part of the part, it will bring difficulty to degreasing. When the polishing paste is small, the surface of the component will be partially overheated and dense spots will appear. After plating, bubbles are easily generated, especially after the plating. Bubbles appear after baking, electroplating, the author often mistakes the substrate material problem: the diameter and rotation speed of the polishing wheel should not be too high, the maximum circumferential speed should not exceed 2 150 m/min: the smaller or complicated parts are 1100~1600 m/min. Low speed: The dense layer on the surface of the part should not be destroyed to prevent and reduce the exposure of the gap below the surface layer, so that it can be lightly thrown.
After fine polishing, it should be separated by soft objects and discharged neatly to prevent bruises and bruises. After polishing, it should be wiped with white powder to remove the residual polishing paste and sent to the plating department for throwing and plating. The pre-plating of zinc alloy die-casting parts is the key in the whole electroplating process. The pre-plating treatment should pay special attention to the concentration and purity of the deionizing liquid. It should be replaced regularly and the washing should be thoroughly clean. When the workpiece is left in the air for a long time, the oxide is easily formed in the water, and it is difficult to completely remove it, resulting in poor bonding force, and the water film in the water may also cause the coating to foam.
Pre-plating should pay special attention to the pre-plated layer to a certain thickness before it can enter the next step of electroplating, as well as bath maintenance. When the workpiece falls into the tank, it should be taken out in time, periodically analyzed, and the tank liquid should be filtered regularly (clearing the tank): if there is a fault in the front plating process, it can be returned to re-de-oiling. If the plating is poor, the plating can be deplated and then plated, and the bright acid should not be plated. After copper or bright nickel, it was discovered that the cause of the defective product was caused by the failure of the front plating, resulting in undue loss.
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