What should be done with zinc alloy products before plating? During the electroplating process of zinc alloy products (qualified components, qualified die-casting technology, and flawless blanks), there are problems such as blistering, low index of bonding force, and corrosion points. Zinc alloy substrates are different from copper substrates and can be deplated, repolished, and replated. At present, there is no ideal deplating agent that can remove copper and nickel from zinc without corroding the substrate. Moreover, the cost of replating is higher and The qualified rate is low. Zinc alloy products will cause scrap due to blistering, poor adhesion and corrosion points in the electroplating. Therefore, to obtain a good coating, pre-plating and pre-plating are the key
1. Polishing: First, the surface should be polished to remove surface burrs, parting lines, flashes and other surface defects. There are three methods: Polishing of the cloth wheel. The particle size of the cloth wheel or continuous tape is 0.045 ~ 0. .069 mm abrasive with butter paste as auxiliary abrasive. The newly-adhered hemorrhoids should be sharpened before use. When the surface of the part is polished by a cloth wheel, the speed should be 1 100 ～ 1400 m / min. It should not be dry during polishing, and the polishing pressure should not be large: this can prevent it. Local overheating of the part and avoid excessive grinding:
Rolling: Rolling and polishing in a roller equipped with abrasive (granite ceramic) and polishing liquid (5% 38 detergent, 3% dewaxing water). The mass ratio of abrasive to parts 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 is better, and the time is 1.5 to 2.0 h.
2. Polishing: Polishing can make the parts level and bright. The overall cloth wheel should be used for polishing. After rough polishing with butter paste and then fine polishing with white oil paste, pay attention to using polishing paste less frequently and frequently.
Because a lot of polishing paste will make the polishing wax stick to the recess of the part, which will make it difficult to remove the oil. When the polishing paste is small, the surface of the component will be overheated locally and dense fine pits will appear. After plating, bubbles are easily generated here, especially after After baking, air bubbles appear and electroplating. The author often mistakes it as a problem with the substrate material: the diameter and speed of the polishing wheel should not be too high, and the maximum peripheral speed should not exceed 2 150 m / min: small or complex parts are used at 1100 to 1600 m / min Low speed: The dense layer on the surface of the part should not be damaged to prevent and reduce the exposure of the gap below the surface layer, so that it is lightly thrown.
After finishing polishing, separate them with a soft object and arrange them neatly to prevent abrasions and bruises. After polishing, wipe it with white powder in order to remove the remaining polishing paste and send it to the electroplating department for instant polishing. Pre-plating of zinc alloy die-casting parts is the key in the whole electroplating process. Pay special attention to the concentration and purity of the degreasing activating solution before the pre-plating treatment. It must be replaced regularly and washed thoroughly. The workpiece is left in the air for a long time, and it is easy to form oxides in the water, which is difficult to completely remove, resulting in poor binding force, and the water film in the water will cause the coating to blister.
For pre-plating, pay special attention to the pre-plated layer to a certain thickness before it can enter the next step of electroplating and plating solution maintenance. The workpieces should be removed in time to the tank, be analyzed regularly, and the tank fluid should be periodically filtered (cleaning the tank): if there is a failure during the pre-plating process, you can return to degrease again. Only after copper or bright nickel was found that the cause of the defective product was caused by the failure of the front plating, which caused unnecessary losses.