1. Water plating

The most common electroplating method is an electrochemical process that uses positive and negative electrodes to apply current in a plating tank. Gold plating, silver plating, nickel plating, chromium plating, cadmium plating, and other electroplating solutions are highly polluted.

2. Coating

Using two specially configured coating liquids, the parts of the metal parts that need to be plated are continuously “brushed”. A chemical reaction occurs in the brushed area, and a coating is accumulated. It is manually operated and used for “feeding” on the workpiece. In order to meet the size requirements, it is often used for the processing of diesel engine crankshafts, connecting rods, etc.

3. Vacuum plating

The metal is heated to about 200 degrees Celsius with electrodes under high vacuum plating, causing the metal to sublimate and produce steam, which adheres to the surface of the plated parts to form a coating. Commonly used metals are cadmium and silver powders, which are often used in glass to produce a mirror effect, such as mobile phone lenses.

4. Sputter coating process

Taking magnetron sputtering as an example, if it is intermittent, the general process is:

1). Surface treatment before plating is the same as evaporation coating;

2). Preparation of the vacuum chamber, including cleaning, inspection, or replacement of the target (no water seepage, leakage, no short circuit with the shield), installation of workpieces, etc.;

3). Vacuum;

4). Magnetron sputtering. Argon gas is usually introduced when the vacuum degree is 0.066~0.13Pa, and its partial pressure is 0.66~1.6Pa. Then turn on the target cooling water and adjust the sputtering current or voltage to the specified value before sputtering. Counting from the time when the sputtering current reaches the current to start sputtering, sputtering will stop, and pumping will stop. This is a general operating situation. In fact, the process conditions used for different materials and products are different and should be determined according to specific requirements. Some conditions must be strictly controlled.

5). Post-plating treatment. Continuous sputtering coating is carried out in separate chambers, that is, the substrate is first transported to a low vacuum chamber, and then successively enters the heating chamber, pre-sputtering chamber, and sputtering chamber under vacuum conditions. After sputtering, the workpiece returns to the low vacuum chamber. vacuum chamber, and finally back to the atmosphere. This coating method has high productivity and can prevent manual misoperation. Product quality is easy to ensure, but the investment is large and it is suitable for mass production.

There are other derivatives of electroplating, such as “rack plating” and “barrel plating”… Wait, it’s just a different way of operating.
The concept of electroplating is the process of plating a layer of other metals or alloys on certain metal surfaces using electrical principles. During electroplating, the coating metal is oxidized into cations and enters the plating solution; the metal product to be plated is used as the cathode, and the cations of the coating metal are reduced on the metal surface to form a coating. In order to eliminate the interference of other cations and make the coating uniform and strong, a solution containing coating metal cations must be used as the electroplating solution to keep the concentration of coating metal cations unchanged. The purpose of electroplating is to apply a metal coating (deposit) on the substrate to change the surface properties or dimensions of the substrate. Electroplating can increase the corrosion resistance of the metal (plated metals are mostly corrosion-resistant metals), increase hardness, prevent wear, and improve conductivity. properties, lubricity, heat resistance, and beautiful surface.

The Role of Electroplating

A technology that uses electrolysis to deposit a metal layer on mechanical products that is well adhered to but has different properties from the base material. The electroplated layer is more uniform than the hot dip layer and is generally thinner, ranging from a few microns to dozens of microns. Through electroplating, decorative protective and various functional surface layers can be obtained on mechanical products, and workpieces with wear and processing errors can also be repaired. The coating is mostly a single metal or alloy, such as target, zinc, brocade, gold or brass, bronze, etc. there are also diffuse layers, such as nickel-silicon carbide, nickel-graphite oxide, etc., and cladding layers, such as those on steel. Copper-chromium layer, silver-steel layer on steel, etc. In addition to iron-based cast iron, steel, and stainless steel, the base materials for electroplating also include non-ferrous metals such as ABS plastic, polypropylene, polyester, and phenolic plastics. However, plastics must undergo special activation and sensitization treatments before electroplating.

Principle of electroplating

In the plating tank containing the electroplating solution, the cleaned and specially pretreated parts to be plated serve as the cathode, and the anode is made of plated metal. The two poles are connected to the positive and negative poles of the DC power supply respectively. The electroplating solution consists of an aqueous solution containing metal plating compounds, conductive salts, buffers, pH regulators, and additives. After energization, the metal ions in the electroplating solution move to the cathode under the action of potential difference to form a plating layer. The metal of the anode forms metal ions in the plating solution to maintain the concentration of metal ions being plated. In some cases, such as chromium plating, an insoluble anode made of lead or lead alloy is used, which only serves to transfer electrons and conduct current. The concentration of chromium in electrolysis must be maintained by regularly adding chromium compounds to the plating solution. During electroplating, the quality of the anode material, the composition of the plating solution, temperature, current density, power-on time, stirring intensity, precipitated impurities, power supply waveform, etc. will all affect the quality of the coating and need to be controlled in a timely manner.
Electroplating methods: Electroplating is divided into rack plating, barrel plating, continuous plating, and brush plating, which are mainly related to the size and batch size of the parts to be plated. Rack plating is used for products of general size, such as car bumpers, bicycle handlebars, etc. Barrel plating is suitable for small parts such as fasteners, washers, pins, etc. Continuous plating is used for series production of wire and strip. Brush plating is used for local plating or repair. Plating solutions include acidic, alkaline, acidic, and neutral rolling solutions with added chromium mixture. No matter what plating method is used, the plating hangers that come into contact with the products to be plated and the plating solution should have a certain degree of versatility. 

Plating classification

Coatings are divided into two categories: decorative protective coatings and functional coatings.
Decorative protective coating is mainly a chromium plating layer on ferrous metals, non-ferrous metals, and plastics, especially a chrome layer on steel, and a layer on zinc and steel. In order to save nickel, people have been able to plate steel with a nickel/iron-high sulfur/iron-low solid content layer. Tin/platings similar to platings can be used on analytical balances, chemical pumps, valves, and flow-measuring instruments.
Functional coatings There are many types of coatings,
like:
1). Sliding bearing cover coatings that improve compatibility and embedding with the journal, lead-tin, lead-tin, lead-steel, and other composite coatings;
2). Used for hard chromium plating on wear-resistant medium and high-speed diesel engine piston rings. This coating can also be used on plastic molds and has the characteristics of a non-stick mold and a long service life.
3). Copper plating on the sliding surface of large herringbone gears can prevent early roughening of the sliding surface.
4). Galvanizing used to prevent steel substrates from atmospheric corrosion:
5). Copper-tin plating to prevent ammonia infiltration:
6). Tin-zinc coating is used for nail welding and preventing galvanic corrosion between steel and aluminum in the manufacture of radios and televisions.
Engineering coatings suitable for repair and manufacturing include chromium, silver, copper, etc. Their thicknesses are relatively large, and the hard chromium layer can be as thick as 300 microns.