Electroplating process: insulation method before local electroplating

During electroplating operation, not all products need electroplating, and some products only need local electroplating. Therefore, we need to master some methods to protect the non electroplating part, and if the first plating surface gets a coating with good adhesion.

There are many insulation methods for local electroplating. The simplest is to overlap and compress the non plated parts of the same parts, and only expose the parts that need to be plated by electroplating equipment. In fact, brush plating and bipolar plating also belong to the scope of local plating.

The encapsulation method is to wrap and block the unplated parts with plastic film strips, adhesive tapes, plastic pipes, rubber plugs, pads and other insulating materials. For example, the unplated parts of the inner hole can be pierced with a plastic pipe slightly larger than the inner hole diameter, or the two ends can be plugged with rubber plugs or pads; For the parts without plating on the periphery, they can be sheathed after scalding with a plastic pipe slightly smaller than the outer diameter, or wrapped with tape. This method is simple and convenient. Its disadvantages are that the parts with complex shape are not easy to wrap, the residual solution in the crevice is difficult to clean, and it is easy to cause mutual pollution between solutions.

Wax insulation is characterized by good adhesion between the insulating layer and the part matrix, and the end edge will not rise during use. It is suitable for parts with high dimensional tolerance requirements on the insulating end edge. In addition, the wax preparation can be recycled. When the service conditions are bad or the working conditions are limited, and it is difficult to use the above methods, all the parts can be plated first, then the parts to be plated can be protected, and then the plating can be removed. In this way, the high temperature and harsh environment can be transformed into room temperature or mild conditions. However, the precision requirement is high. The parts not plated are not allowed to contact acid, alkali and other chemical reagents. This method cannot be used.

If two or more plating layers are required for some batches of electroplated parts or one part, for example, when local plating is carried out on the scribed part of the stainless steel vernier caliper, a profiling fixture that only exposes the scribed part can be made of acid and alkali resistant polypropylene plastic, and the end face is equipped with an appropriate auxiliary cathode, so that local chromium plating can be carried out conveniently. Some special parts can also be made into a imitation box, which only exposes the parts to be plated. With the auxiliary anode and local chromium plating, the effect is very good.

Non metallic parts can be coated with plating paint: for plastics that are difficult to activate and electroplate (such as polyvinyl chloride), a layer of paint that is easy to activate and electroplate can be coated on the surface to be plated. Coating and stopping plating paint: in contrast to the use of plating paint, this method is to use paint materials that are difficult to activate and electroplate. Coating toxic paint: it is prepared by adding about 10% sulfide into ordinary insulating paint. When in use, it is coated on the parts to be insulated. When the parts are activated and electroless plated, due to the catalytic toxicity of the toxic paint, these coated parts cannot undergo electroless plating process and play a role of local insulation