In order to reduce weight, aluminum alloy parts are widely used in aviation industry. After surface strengthening by electroless nickel plating, it is not only corrosion-resistant and wear-resistant, but also weldable. For example, the service life of piston head of stroke engine is improved by electroless nickel plating. Other measures such as electroless nickel plating with low stress and compressive stress are adopted for titanium alloy parts and beryllium alloy parts.
Nickel+thallium+boron ternary alloy electroless plating (NTB) has been designated as the surface strengthening process for more than 0/60 parts of Pratt & Whitney jet engine to resist wear and fretting wear. For example, NTB electroless plating is used to seal the main shaft of jet engine. The US Air Force requires engine manufacturers to provide 4,000 tactical cycles. When the wear reaches 0. 178mm, it must be dismantled and rebuilt. After NTB electroless plating, the wear of spindle sealing surface is significantly reduced, and the wear amount is about 0.008 mm after 4000 tactical cycles.
Metal mirrors are widely used in aerospace systems. The substrate is beryllium or aluminum with high strength and light weight, and the surface is strengthened by special electroless nickel plating. This electroless nickel plating with phosphorus content of 12.2% ~ 12.7% can be polished to 9? With such high precision, it has excellent performance in the space where low inertia is needed.
Although the chemical plating industry in China started late, since 1990s, with the unremitting efforts of various scientific research units, it has formed mature technology and experience, and built a chemical nickel plating processing line for aircraft parts in Luoyang, China. Solving the problem of using mixed fuel of ethanol and gasoline is one of the development trends of automobile industry. The use of mixed fuel, in addition to performance problems, will also produce fuel system corrosion problems. In Brazil, using ethanol as fuel and applying electroless nickel plating technology to protect zinc die castings (such as vaporizers) from corrosion has become a process specification. In the United States, when methanol or the mixed fuel of methanol and gasoline is widely used, electroless nickel plating is bound to be used as a surface protection means for carburetor and fuel pump system in automobile industry.
Differential planetary gear is an important part of automobile. It is plated with a 25 micron thick electroless nickel layer to improve wear resistance. Some automobile manufacturers use PTFE composite electroless nickel plating process on shafts. This composite coating not only has a certain hardness, but also has good lubrication performance, which improves the service life of the shaft.
The automobile industry takes advantage of uniform electroless nickel plating to protect complex parts such as gears, radiators and fuel nozzles. The aluminum radiator with electroless nickel plating of about 10um has good weldability. After electroless plating on gears, the dimensional error is easily kept within 0.3 ~ 0.5 um. However, if electroplating process is adopted, it must be machined after plating to reach the acceptable tolerance range. Electroless nickel plating on fuel injector can provide good corrosion resistance and wear resistance of fuel. Usually, the corrosion and wear of fuel will lead to the enlargement of the injection hole, so the injection quantity will increase, which will make the horsepower of the automobile engine exceed the design standard and accelerate the engine damage. Electroless nickel plating can effectively prevent the corrosion and wear of injectors and improve the reliability and service life of engines. In chemical industry, electroless nickel plating technology is used to solve the corrosion problem instead of expensive corrosion-resistant alloy, so as to improve the purity of chemical products, protect the environment, improve the safety of operation and the reliability of production and transportation, and thus obtain more favorable technical and economic competitiveness.
Electroless plating is widely used to protect the inner wall of large reaction vessels. At first, an interesting application example was 1955. General Transportation Company (GATX) used electroless plating to protect the inner wall of tank car to prevent alkali corrosion. Nowadays, the technology of electroless nickel plating has made great progress, which can provide reliable protection in various chemical corrosive environments.
The most extensive application of electroless nickel plating is valve manufacturing. Ball valves, gate valves, rotary valves, check valves and butterfly valves made of steel can be plated with 25 ~ 75um high phosphorus electroless nickel to improve corrosion resistance and service life. The influence of electroless nickel plating on chemical pump is also significant. Valves working under alkaline corrosion conditions should be electroless nickel plated with low phosphorus content of 1% ~ 2%. Because the annual corrosion rate of low phosphorus electroless nickel plating layer is about 2.5um under caustic corrosion conditions, which is better than that of medium phosphorus or high phosphorus electroless nickel plating layer. Electroless nickel plating layer is not resistant to corrosion in strong oxidizing acids such as concentrated nitric acid and concentrated sulfuric acid. Although the corrosion rate in hydrochloric acid is lower than that in austenitic stainless steel, the corrosion resistance is still insufficient. Therefore, electroless nickel plating is not suitable for the above-mentioned strong acid medium, or the medium that may be hydrolyzed to generate the above-mentioned strong acid. Replacing stainless steel fasteners with 25 ~ 50μ m thick high phosphorus electroless nickel plating layer not only overcomes the stress corrosion cracking problem of austenitic stainless steel, but also saves a lot of money. The inner wall of the pressure vessel for producing low-density polyethylene is 25um to prevent iron pollution and discoloration of polyethylene. If it is stainless steel, the price is about twice that of electroless plating. Oil and natural gas are one of the important markets for electroless nickel plating, and electroless nickel plating technology is widely used in oil production and oil pipeline equipment in oil fields. The typical corrosive environment of petroleum and natural gas industry is underground brine, carbon dioxide and hydrogen sulfide, and the temperature is as high as 170 ~ 200℃, accompanied by the erosion of sediment and other abrasive particles. And the corrosive environment is quite bad. Under such harsh conditions, the life of low carbon steel oil and gas pipeline is only 2 ~ 3 months. After being protected by 50 ~ 100 μm thick high phosphorus electroless nickel plating layer, its corrosion rate is reduced to the level equivalent to that of Hastelloy. Considering the high price of corrosion-resistant alloy, the technical and economic performance of carbon steel pipeline protected by electroless nickel plating is the best from the perspective of cost performance.
Pump shell, impeller, outlet pipeline and other oil and gas pump parts are electroless nickel plated according to different corrosive environments, and the thickness of nickel plating varies from 25 to 75 um, which has excellent anti-corrosion effect. Electroless nickel plating on oil pump is an ideal application example: in West Texas Oilfield, the life of oil pump protected by electroless nickel plating is more than 4 years, and that of unprotected oil pump is less than 6 months. The electroless nickel plating layer is corrosion-resistant and wear-resistant. Because of the high uniformity of the electroless nickel plating layer, the oil pump barrel can be made into an integral part, thus significantly improving the quality of the oil pump and reducing the production cost. In the oil field, high phosphorus electroless nickel plating is widely used on the heater surface of oil-water separation device to prevent corrosion, and the thickness of the coating is usually 25 ~ 75um. The valves, pipe joints and pipe hoops of the gathering and transportation device are also protected by electroless nickel plating. The food processing industry provides a huge potential market for the application of electroless nickel plating. Electroless nickel plating is called a potential market because there are obstacles in its wide application in food industry. For example, in the United States, the FDA (American Food and Drug Administration) has not yet formulated regulations and standards for the application of electroless nickel plating in the food industry; Usually, FDA will approve the application of electroless nickel plating in direct contact with food according to the specific circumstances. The main reason is that the classical electroless plating solution contains toxic heavy metal ions such as lead and cadmium as stabilizers. However, many modern electroless nickel plating solutions no longer use heavy metal ions as stabilizers; Obviously, this obstacle will be removed sooner or later. Parts in food packaging machinery that are not in direct contact with food, such as bearings, rollers, conveyor belts, hydraulic systems and gears, are typical applications of electroless nickel plating in food industry.
In the process of food processing, corrosive media such as salt water, nitrite, citric acid, acetic acid, natural wood fumigation and volatile organic acids will be involved. The food processing temperature is between 60 ~ 200, and the relative humidity of the production environment is very high. Under this condition, food processing equipment will have problems such as metal corrosion, fatigue and wear. For the metal surface in contact with food, the traditional protection method is electroplating hard chromium; However, in the acid medium containing chloride ion, the corrosion resistance of chromium plating layer is not good; Electroless nickel plating has obvious advantages in coating uniformity, high corrosion resistance, anti-sticking and demoulding. Electroless nickel plating on the parts in contact with food on the dough mixer is one of the successful examples. Electroless nickel plating is increasingly used in food filling machines, screw feeders, stirring pots, food molds, baking pans, ovens, bread holding furnaces and other food machinery. The environmental conditions of mining industry are harsh, and underground machinery inevitably comes into contact with salt water and mineral acid to withstand the test of corrosion and wear. Therefore, mining machinery needs surface protection.
In the mine roof support system, electroplated hard chromium is often used as the anti-corrosion and wear-resistant protective layer of hydraulic prop. However, due to cracks and pores on the surface of hard chromium, hydraulic props are often bitten to death due to serious corrosion in use. This problem of high-pressure hydraulic cylinder is more serious. Under high pressure, the coating was stretched, which further aggravated the cracking of hard chromium layer with high internal stress. In this case, when the hydraulic prop is stretched under high pressure, the electroless nickel plating layer with a compressive stress of 25um will not crack and can withstand the corrosion and wear of the underground environment of coal mine.
In some open-pit mining production, such as phosphate rock used as fertilizer, high-pressure pump and jet pump nozzle are used. At this time, the corrosion and erosion problems are quite serious, but the application of corrosion-resistant and wear-resistant electroless nickel coating can prevent premature damage of mechanical parts. Electroless nickel plating technology has been widely used in the military, such as electroless nickel plating protection of aircraft ejection cover and orbit on aircraft carrier. The working environment of the ejector is very bad. Due to the high temperature airflow scouring the orbit during aircraft launch, the great force during ejection and the corrosion of marine climate conditions, the ejection system can only be used for 6 ~ 12 months. At present, the surface treatment technology adopted is: correctly pretreating the fume hood, electroplating nickel, electroless nickel plating 100um, cadmium plating 12.5um, and chromic acid passivation. This composite coating has good wear resistance and micro-vibration wear resistance, and the service life of the ejection system can be extended to 14 ~ 18 years, which is 0/8 times that of/kloc-0.
The trunnions of military vehicles have been protected by electroless nickel plating for many years to prevent corrosion and wear of road mud and salt water.
Tank rearview mirror is made of aluminum, and after fine grinding and polishing, electroless nickel plating is used as a corrosion-resistant and wear-resistant protective layer. The mirror is required to have a reflectivity of 80% in the visible spectrum, and electroless nickel coating can easily meet these optical requirements. The aluminum radar waveguide is coated with a 25 micron thick electroless nickel coating to prevent corrosion on land and in the sea. The uniformity of electroless nickel plating can meet the technical requirements of various waveguides. Electroless nickel plating is widely used in electronic and computer industries, involving almost every electroless nickel plating technology and process. According to the development of electronics and computer industry, many new electroless nickel plating processes and materials have been developed. In terms of technical performance, besides corrosion resistance and wear resistance, it also requires weldability, non-proliferation, electrical performance and magnetic performance.
Some countries have enacted laws and regulations requiring that electronic equipment must be shielded to prevent electromagnetic and radio frequency interference. The bimetallic structure coating with copper plating and electroless nickel plating on the plastic shell of electronic equipment is recognized as one of the most effective shielding methods. Electroless nickel plating is one of the key steps in manufacturing computer thin film hard disk. Ni-P alloy layer with the thickness of 65438 02.5 μ m was plated on the surface of the finished 5086 Mg-Al to prepare for the subsequent vacuum sputtering magnetic recording film. The phosphorus content of electroless nickel plating layer is 12%wt (about 20.5% at). The coating must be low stress and compressive stress. After heating 1h at 250℃ or 300℃, it remains nonmagnetic, that is, the remanence is less than 0. 1× 10-4t. The coating must be uniform and smooth, and any defects and protrusions on the surface should not exceed 0.025um. Due to the high technical requirements, it is necessary to use special electroless plating solution with high quality and high cleanliness, automatic electroplating control equipment and high cleanliness workshop environment. Electroless nickel plating on computer thin film hard disk is a typical representative of high-tech electroless nickel plating, which occupies a very important market share.
The application of electroless nickel plating technology in microelectronic device manufacturing industry is growing rapidly. It is reported that Xerox adopted selective electroless nickel-phosphorus alloy plating technology in the interconnection of VLSI multilayer chips and the filling and leveling of vias. Its products have passed the tests of shear strength, tensile strength, high and low temperature cycling and various electrical properties. Practice shows that the application of electroless nickel plating technology improves the technical economy of microelectronic device manufacturing process and the reliability of products. Injection molding machines, die-casting molds and other molds are a large number and wide range of products in machinery and light industry. Because of the complex geometry of the mold, when the surface of the mold is strengthened by electroplating, in order to electroplate all the surfaces, complex auxiliary anodes and hangers must be designed and installed. Moreover, post-plating machining is needed to ensure dimensional accuracy and surface roughness requirements; Moreover, electroless nickel plating is one of the most economical and effective die surface treatment technologies because of its low friction coefficient and outstanding demoulding performance.
Moulds and core boxes for casting are usually cast iron or cast aluminum parts, which will be worn out in the process of use and will be scrapped soon. After using electroless nickel plating to protect the surface, the quality of casting model and core box is graded, and the service life is significantly improved.
The rotating speed of textile machinery is very high, and various fiber yarns wear the mechanical parts seriously. Electroless nickel plating, especially synthetic polycrystalline diamond composite electroless plating technology, has successfully solved the wear problem of textile machinery parts.
All kinds of rollers and parts on the printing press are protected by electroless nickel plating with a thickness of 25 ~ 50um, which can prevent the corrosion of ink and whitening solution. The high uniformity of electroless nickel plating ensures the dimensional accuracy of printing roller, and there is no need for mechanical processing after plating.
Some medical instruments, such as surgical forceps, dental drills, medical molds and other metal products, have been replaced by electroless nickel plating.