Electroplating is the process of plating a thin layer of other metals or alloys on the surface of certain metals using the principle of electrolysis. Metal oxidation (such as rust), improve wear resistance, electrical conductivity, reflectivity, corrosion resistance (copper sulfate, etc.) and enhance aesthetics. The outer layers of many coins are also electroplated. Electroplating is a material surface treatment process, which uses the chemical reaction principle of electrolysis to spread a layer of metal on the surface of a conductor. Common types of electroplating are chrome plating, nickel plating, copper plating, zinc plating, etc.

What are the types of electroplating?

A, By coating types:

①Single metal coating has more than ten kinds of zinc, cadmium, copper, nickel, chromium, tin, silver, gold, iron, cobalt, etc.

②There are dozens of alloy coatings such as copper-tin, zinc-copper, zinc-iron, nickel-cobalt, nickel-iron, zinc-tin-iron, tin-zinc-antimony, tin-zinc-cobalt, etc.

B, By applications:

① Protective coating: coatings such as Zn, Ni, Cd, Sn and Cd-Sn are used as anti-corrosion coatings for atmospheric and various corrosive environments;

② Protective decorative coating: such as Cu-Ni-Cr, Ni-Fe-Cr composite coating, etc., both decorative and protective;

③ Decorative coating: such as Au, Ag and Cu. Sun imitation gold coating, black chrome, black nickel coating, etc.;

④Reparative coating: For example, electroplating Ni, Cr, Fe layer to repair some high-cost wear parts or processing out-of-tolerance parts;

⑤ Functional coatings: conductive coatings such as Ag and Au; magnetic conductive coatings such as Ni-Fe, Fe-Co, Ni-Co; high temperature anti-oxidation coatings such as Cr and Pt-Ru; reflective coatings such as Ag and Cr; black chrome, Anti-reflective coatings such as black nickel; hard chrome, Ni. SiC and other wear-resistant coatings; Ni. VIEE, Ni. C (graphite) anti-friction coating, etc.; Pb, Cu, Sn, Ag and other weldable coatings; anti-carburizing Cu coating, etc.

What are the electroplating methods?

Electroplating is divided into rack plating, barrel plating, continuous plating and brush plating, which are mainly related to the size and batch of the parts to be plated. Rack plating is suitable for general-sized products, such as car bumpers, bicycle handlebars, etc. Barrel plating is suitable for small parts such as fasteners, washers, pins, etc. Continuous plating is suitable for mass-produced wire and strip. Brush plating is suitable for partial plating or repair. The electroplating solution includes acid, alkaline and acid and neutral solution with chromium compound. No matter what kind of plating method is used, the plating tank and hanger in contact with the product to be plated and the plating solution should have a certain degree of resistance. Universality.

How does electroplating work?

Electroplating requires a low-voltage, high-current power supply to supply the electroplating bath and an electrolytic device consisting of the electroplating solution, the part to be plated (cathode), and the anode. The composition of the electroplating solution varies depending on the plating layer, but all contain the main salt that provides metal ions, the complexing agent that can complex the metal ions in the main salt to form complexes, the buffer used to stabilize the pH of the solution, the anode activator and Special additives (such as brighteners, grain refiners, levelers, wetting agents, stress relievers and fog suppressants, etc.). The electroplating process is a process in which the metal ions in the plating solution are reduced to metal atoms by the electrode reaction under the action of an external electric field, and the metal is deposited on the cathode. Therefore, it is a metal electrodeposition process that includes steps such as liquid phase mass transfer, electrochemical reaction, and electrocrystallization.

In the plating tank containing the electroplating solution, the cleaned and specially pretreated part to be plated is used as the cathode, and the anode is made of plated metal, and the two poles are respectively connected with the negative and positive poles of the DC power supply. The electroplating solution is composed of an aqueous solution containing metal-plating compounds, conductive salts, buffers, pH adjusters and additives. After electrification, the metal ions in the electroplating solution move to the cathode under the action of the potential difference to form a plating layer. The metal of the anode forms metal ions into the electroplating bath to maintain the concentration of metal ions being plated. 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 plating solution. During electroplating, the quality of the anode material, the composition of the electroplating solution, temperature, current density, energization time, stirring intensity, precipitated impurities, power supply waveform, etc. will affect the quality of the coating, which needs to be controlled in time.

There are six elements in electroplating solution: main salt, additional salt, complexing agent, buffer, anode activator and additives.

The electroplating principle includes four aspects: electroplating solution, electroplating reaction, electrode and reaction principle, and metal electrodeposition process.

What is electroplating used for?

The technology of depositing well-adhered metal coatings on mechanical products using the electrolytic cell principle, but with different properties and substrate materials. The electroplating layer is more uniform than the hot-dip layer, and is generally thinner, ranging from several microns to tens of microns. Through electroplating, decorative protective and various functional surface layers can be obtained on mechanical products, and parts that are worn and machined incorrectly can also be repaired.

In addition, there are different functions according to various electroplating needs. An example is as follows:

1. Copper plating: used as a primer to improve the adhesion and corrosion resistance of the electroplating layer. (Copper is easy to oxidize. After oxidation, the patina is no longer conductive, so copper-plated products must be protected by copper)

2. Nickel plating: used as a primer or for appearance, to improve corrosion resistance and wear resistance, (among which chemical nickel is the modern technology in which the wear resistance exceeds that of chrome plating). (Note that many electronic products, such as DIN heads and N heads, no longer use nickel as the base, mainly because nickel is magnetic, which will affect the passive intermodulation in the electrical performance)

3. Gold plating: Improve conductive contact resistance and improve signal transmission. (Gold is the most stable and most expensive.)

4. Palladium-nickel plating: Improves conductive contact resistance, improves signal transmission, and has higher wear resistance than gold.

5. Tin and lead plating: improve the welding ability, and will be replaced by other substitutes soon (because most of the lead is now plated with bright tin and matte tin).

6. Silver plating: Improve conductive contact resistance and enhance signal transmission. (Silver has the best performance, easy to oxidize, and also conducts electricity after oxidation)