Under the catalysis of catalyst iron, hypophosphite in solution is catalytically dehydrogenated on the catalytic surface to form active hydride, and the hydride is oxidized to phosphite. Active hydride reacts with nickel ions in solution to deposit nickel, and nickel itself oxidizes to hydrogen. Namely:

2h2po 2-+2H2O+Ni2+→Ni0+H2 ↑+ 4h++ 2hpo 32-.

At the same time, part of hypophosphite in the solution is reduced to elemental phosphorus by hydride and enters the coating. Namely:

H2PO2-+[H+] (catalytic surface) →P+H2O+OH-, and the chemical coating is an amorphous flake NiP alloy. A method of depositing a layer of nickel on the surface of metal parts by redox action without external current. Used to improve corrosion resistance and wear resistance, increase luster and beauty. Suitable for bright nickel plating of tubular or complex small parts without polishing. Generally, the plated parts are immersed in the mixed solution of nickel sulfate, sodium dihydrogen hypophosphite, sodium acetate and boric acid, which changes at a certain acidity and temperature. Nickel ions in the solution were reduced to atoms by sodium dihydrogen hypophosphite and deposited on the surface of the parts, forming a fine and bright nickel coating. Steel parts can be directly plated with nickel. Tin, copper and copper alloy parts should be in contact with aluminum plate for 1-3 minutes to accelerate electroless nickel plating.

Electroless plating is a method to obtain metal alloy with catalytic surface on the plated parts through redox reaction without electricity. This is a newly developed new technology. Compared with electroplating, the history of electroless nickel plating is relatively short, and its real industrial application abroad was in the late 1970s and early 1980s. In 1844, A.Wurtz found that metallic nickel can be deposited from the aqueous solution of metallic nickel salt by hypophosphite reduction. The real discovery and application of electroless nickel plating technology has been found in 1944. The discovery of A.Brenner and G.Riddell of American National Bureau of Standards clarified the catalytic characteristics of coating formation, and found the method of depositing non-powder nickel, which made the industrial application of electroless nickel plating technology possible. However, the electroless nickel plating solution at that time was extremely unstable, so it was of no practical value in a strict sense. The application of electroless nickel plating process is nearly ten years later than the laboratory research results. After World War II, American General Transportation Company became interested in this process. They want to plate nickel on the inner surface of caustic soda barrel, but ordinary electroplating method can't achieve it. Five years later, they researched and developed the technology of electroless nickel-phosphorus alloy plating, and published many patents. 1955, their first experimental production line was built and a commercially useful electroless nickel plating solution was made. The commercial name of this electroless nickel plating solution is "Kanigen". In foreign countries, especially the United States, Japan and Germany, electroless nickel plating has become a very mature high-tech and widely used in various industrial sectors.

The industrial production of electroless nickel plating in China started late, but it has developed rapidly in recent years. Not only published a large number of papers, but also held a national electroless plating conference. According to the statistics of articles published in the fifth annual meeting of electroless plating, there are more than 300 manufacturers, but this number should be extremely conservative at that time. It is speculated that the total scale of electroless nickel plating market in China should be about 30 billion yuan every year, and it will develop at the rate of 10% ~ 15% every year.