When cast iron workpieces are treated with alkaline zinc-nickel alloy additives, due to their special processing, complex structure, and the fact that the surface of cast iron is prone to rust, which is difficult to handle after rusting and has poor decorative properties, it is necessary to improve their surface performance during the electroplating process. In view of the particularity of cast iron, the following three points should be noted during electroplating.
1.During the high-temperature casting process, a non-conductive oxide film forms on the surface of cast iron, which hinders the deposition of the zinc-nickel alloy coating. Therefore, the oxide scale on the surface of the workpiece should be thoroughly removed before electroplating. Bigley suggests using shot blasting machines to polish the surface. This not only effectively removes the oxide scale but also causes the high-carbon layer formed during casting to fall off, resulting in micro-roughness and facilitating the improvement of the adhesion of the coating.
2. The structure of cast iron substrate is loose and porous, with a large number of sand holes. The surface is loose and uneven, so the surface area is much larger than the macroscopic area, resulting in the actual current density being much smaller than the displayed current density. Therefore, during the electroplating of zinc-nickel alloy, the current density should be 1 to 2 times greater than that of other steel substrates. Only by instantaneously activating the surface through the impact of a large current can the loose surface be covered by a dense coating.
3. The acid washing and ultrasonic cleaning processes should be strengthened. Due to the fact that a large amount of grease, lubricating oil and coolant remain in cast iron parts during processing, as well as the insoluble contaminants such as oxide films formed by sand grains and iron filings from the mold during storage, and cast iron parts themselves contain a large amount of graphite, it is necessary to strengthen the pretreatment processes such as acid washing and ultrasonic cleaning when electroplating zinc-nickel alloys. Only in this way can a uniform, clean, well-conductive and easily electroplated zinc-nickel alloy coating be formed.
About us
Guangdong Bigely Technology Co., Ltd. ,founded in 2003, is a high-tech enterprise integrating R & D，production, sales and service, specializing in the production of electroplating chemicals. As a fast growing electroplating chemicals supplier in China, our products are widely used to meet the plating needs of different industries and exported to many countries from all over the world. They can meet the environmental protection standard after use, mainly used in automobile parts, sanitary ware, electronic products, hardware, furniture, building accessories and other fields.
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