Galvanic coating (or electroplating) is the process of deposition of particles of one metal on another by electrolysis. This type of service is intended for both decorative and use as corrosion protection or surface hardening.
The most common types of coatings are zinc, copper, chrome and nickel, but there are also, exceptionally decorative coatings where, as a protective surface, a thin layer of gold or silver is deposited to give the product an attractive appearance.
Galvanization is widely used in engineering, aerospace, medicine, jewelry, etc. The process consists of immersing a metal workpiece into an electrolyte container with the desired coating, which is anode, which in turn is cathode. Then, after switching on the DC generator, the deposition of one metal on another occurs.
Any type of application, the following types are distinguished:.
- Drum – effective for coating small technical articles in large quantities, but not acceptable for decorative parts, due to their constant friction between them and the formation of microscratches.
- Frame – parts are fixed in so-called “frames” made of copper or brass. Efficient for dimensional and critical parts, which affects the higher cost of the process..
- Continuous – passing at a certain speed of long parts, such as tubes, wire, etc. of the container with negatively charged electrolyte.
The main types of galvanic coatings can be attributed to the following:.
- Plain Corrosion Resistant is the cheapest type of coating used in mass production. Most often, as an electrolyte, zinc is used and the process is called – galvanizing.
- Decorative is a type of coating used exclusively for decorative purposes. This category may include chrome plating, silver plating, gilding, and nickel plating.
- Functional coatings – coatings that are an integral part of the process of manufacturing parts. These include silver and gold-plating, to increase electrical conductivity; hard chrome plating, to increase the wear resistance of parts; iridescent galvanizing, due to its electrical insulating properties; tinning, tin-bismuth and many others.
- Special – a type of durable coatings for heavy duty applications, such as metal cutting. The most common are titanium (Ti), cobalt (Co), aluminum oxide (Al2O3) and others, and their combinations.
Chemical oxidation (black oxide)
Chemical oxidation (blackening) is a technological process of creating a protective layer on the steel surface in the form of a finely crystalline microporous oxide film, which:
- serves as a barrier that protects the metal from the environment and prevents corrosive processes caused by contact with water, water vapors or slightly aggressive substances;
- provides dimensional stability for the product, as the layer thickness does not exceed 5 µm
is aesthetically pleasing and, in some cases, can serve as a good base coat for subsequent painting.
Oxidation is a multi-stage process. The technology of application of oxide films on carbon and low-alloy steels provides sequential degreasing, etching, activation, nielloding and sealing, with thorough washing of the workpiece after each stage. As a result of sequential immersion of products in containers with reagents and special solutions, a layer is formed on the metal surface, which consists of magnetic iron oxides.
The benefits of chemical oxidation.
What gives ink in practice? Protective coatings obtained by chemical oxidation method using modern technologies allow storing or using steel products and parts for a long time without fear of corrosion.
This technology is recommended for use in mating parts, due to the stability of the coating, as it does not peel off, has a low wear coefficient and does not form scoring..
After the blackening, metal parts acquire a deep saturated black color by forming a uniform oxide film over all surfaces of the processed product. Thus, the appearance depends on the roughness of the surface: Chemical oxidation of polished metal gives a black gloss. Black matt black ensures that the parts that have been sandblasted.
The process has a number of advantages over alternative methods of steel blackening (for example, dipping hot steel parts into oil-containing mixtures). Processing in special solutions and reagents provides increased wear resistance by forming a protective layer of optimal thickness with excellent anticorrosive properties, strength and resistance to abrasion. Chemical blackening is a “cold” process. This technology can process parts that can not be heated due to the risk of deformation or warping in the process of increasing temperature and subsequent cooling. In the process of chemical oxidation dimensions of metal products do not change, which is very important in terms of surface strength and corrosion protection of precision parts manufactured with high requirements for precision manufacturing and tolerances, including threaded connections or gear teeth.
Our company works according to the modern technologies and uses exclusively high quality chemical reagents that provide excellent metal processing results, corrosion resistance of protective coatings and deep black color of surfaces.
Technological capabilities of the enterprise allow to perform chemical treatment of large parts. The maximum size of processed products is 700×700×400 mm. The company carries out orders for the inking of any forged, stamped and milled parts.
We are ordered to apply protective coatings by chemical and electrochemical methods on: cutting tools for metal, woodworking and grinding processes; units and parts of machines and mechanisms; housing parts of industrial equipment; fasteners (bolts, nuts, studs, washers and other metalware).
- Dip galvanizing