1. Concept
Electroplating is to electrodeposit one or more layers of metal coating on the surface of the workpiece to give the workpiece a beautiful appearance or specific functional requirements. During electroplating, the coated metal or other insoluble materials are used as the anode, the metal products to be plated are used as the cathode, and the cations of the coated metal are reduced to form a coating on the metal surface. In order to eliminate the interference of other cations and make the coating uniform and firm, it is necessary to use a solution containing metal cations as an electroplating solution to keep the concentration of metal cations in the coating unchanged. The purpose of electroplating is to coat a metal coating on the substrate to change the surface properties or dimensions of the substrate. Electroplating can enhance the corrosion resistance of the metal (coated metal is mostly corrosion-resistant metal), increase hardness, prevent wear, improve electrical conductivity, lubrication, heat resistance, and surface beauty.
2. Principle
In the plating bath containing electroplating solution, the cleaned and specially pre-treated parts to be plated are used as the cathode, and the plated metal is used as the anode, and the two poles are respectively connected with the negative and positive terminals of the DC power supply. Electroplating solution consists of an aqueous solution containing plated metal compounds, conductive salts, buffers, pH regulators and additives. After electrification, the metal ions in the plating solution move to the cathode to form a coating under the action of potential difference. The anode metal forms metal ions into the plating solution to maintain the concentration of the coated metal ions. In some cases, such as chrome plating, it is an insoluble anode made of lead and lead-antimony alloy, which only plays the role of transferring electrons and conducting current. The concentration of chromium ions in the electrolyte is maintained by regularly adding chromium compounds to the bath. During electroplating, the quality of the anode material, the composition of the plating solution, temperature, current density, energized time, stirring intensity, impurities precipitated, and power waveform will affect the quality of the coating, which needs to be controlled in time.
3. Function
Technique for depositing a metal coating on a mechanical product with good adhesion but different properties than the base material by electrolysis. The electroplating layer is more uniform than the hot dip layer and is generally thinner, ranging from a few microns to tens of microns. Through electroplating, it is possible to obtain decorative protection and various functional surface layers on mechanical products, and it is also possible to repair worn and machining errors of the workpiece. The coating is mostly a single metal or alloy, such as titanium target, zinc, cadmium, gold or brass, bronze, etc. There are also dispersion layers, such as nickel-silicon carbide, nickel-fluorine fossil ink, etc. There are also cladding layers, such as the copper-nickel-chromium layer on steel and the silver-indium layer on steel. In addition to iron based cast iron, steel and stainless steel, there are non-iron metals such as ABS plastics, polypropylene, polysulfone and phenolic plastics, but plastic plating must be subjected to special activation and sensitization treatment.