As a result of its undeniable advantages and specific qualities, chemical nickel plating can be used in automobile manufacturing, instrument engineering and in many other branches of production sector.
The most important among them is the fact that chemical nickel plating has high protective qualities and it is more effective to aggressive environment in comparison with electroless nickel.
The technology provides more qualitative covering of not only the products of metal, cast iron, plastic but of inorganic dielectrics which include ceramics, glass, porcelain, glimmer, ceramized glass and ferrites.
Advantage: offered technology has high effectiveness and quality and is profitable economically
The technology allows electroless nickel plating of ferrous and alloy steels, cast iron articles, as well as for coating of plastic, glass, ceramics, and so on.
Electroless nickel plating is widely implemented thanks to the valuable properties of its coating:
– high uniformity,
– high hardness,
– significant corrosion resistance and wear resistance.
Electroless nickel plating has higher protective properties than nickel electroplating.
Protective properties of electroless nickel plating are defined not only by their own chemical resistance of the deposited metal, but by its structural features.
Electroless-reduced nickel after may be used to cover wear parts and the parts which operate under high temperature conditions.
It is found that the electroless nickel plating is less porous than electroplating of the same thickness.
Determining porosity of nickel plating of different thickness, it was found that under porosity parameter electroless-reduced Ni-plating 8-10mm thick corresponded to electrolytic precipitations 20 microns thick.
It should also be noted that the plating obtained by electroless method contain hydrogen several times less than electroplating.
The ability to protect the main material against corrosion under the following conditions is important for nickel-coated products:
– at high temperatures (560-625°C)
– and the pressure of 1250 MPa, in the air and steam environments.
Because of its specific properties nickel-plating finds application in many fields of mechanical and instrument engineering:
– coating of metal articles of complex profile (with deep channels and blind holes);
– to improve wear resistance of wearing surfaces of machine parts;
– to improve corrosion resistance in boiling alkali media;
– to replace chromium coating (with subsequent thermal treatment of electroless nickel);
– to use cheaper steel with chemical nickel plating instead of corrosion-resistant steel;
– for nickel plating of large-size equipment;
– for coating of plastics, glass, ceramics and etc..
There were conducted comparative tests of nickel plated coatings.
Under conditions of these test there was proved – that the products coated with nickel by electroless method have higher protective capacity than those coated by electroplating method.
Conducted tests showed that Ni-coated samples of 25 micron thick do not change their appearance after spraying them with a solution of sodium chloride in the corrosion chamber over 8 days; after spraying outdoors – over 80 days; in water, heated up to 82°C (with air blow) – for 42 days.
Also as a result of the tests of electroless nickel plating and nickel electroplating regularly sprayed in a corrosion chamber with 3% sodium chloride solution, there was proved – that the corrosion pits appear on electroless coatings, but further surface damage does not take place even after 2000 hours of tests, while they spread quickly coatings made by electroplating.
Additionally, for purposes to compare the use of electroless nickel plating to protect the parts against corrosion under conditions of tropical climates, we used steel samples which were coated in solution.
– And also samples with coatings made by nickel electroplating (matte-finished and glazed-finished).
The samples were placed in a chamber for 21 hours at a temperature of 35 ± 2 and 20 ± 2°C.
The first corrosion pits on the samples with coating made by nickel electroplating showed up on the matte-finished nickel -in 7 day after testing, on glazed-finished nickel – in 14 days.
Corrosion pits occurred on none of the samples with coating made by electroless nickel plating within 84 days of testing.
In 14 days a thin purple film occurred on them and remained until the end of testing. By assumption of scientists the presence of this film contributed to enhancing of the corrosion resistance of these coatings.
Testing the samples under conditions of sub-tropical climate, indoor with humidity and temperature of the outer atmosphere, – coating made by electroless nickel plating were also covered with an oxide film of purple color and it remained within two years.
It should be added that with the help of electroless nickel plating the problem of creation of light and wear-resistant friction pairs made of different aluminum alloys can be solved.
Electroless nickel plating may be used to coat non-metallic materials (plastics and inorganic dielectrics).
Inorganic dielectrics include ceramics, glass, porcelain, mica, glass ceramics, and ferrites.
Metallization of inorganic dielectrics is used to make the following surface properties to the metal parts:
– Ability to soldering,
– Thermal conductivity.
Metallization of glass is used to produce mirrors. Silicate materials (glass, quartz, glass ceramics, mica, etc.) at first are subject to chemical degreasing, and then are treated in a special solution.
Parts made of non-metallic materials with metal coatings are widely introduced in radio engineering, automotive and other industries, so the question of the methods of electroless plating of metals combined with galvanic one is up-to-date.
If you are interested – we will provide additional information and designer’s supervision over implementation of the technology.
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