Sodium hypophosphite CAS No. 7681-53-0 (NaPO2H2) is an ideal reducing agent mainly used in chemical plating, electroplating, organic synthesis industry, food processing and preservation, and as a stabilizer for engineering plastics. With the deepening of research and the significant increase in its derivatives, its application fields continue to expand, making it an important inorganic salt product.
Properties of Sodium Hypophosphite (NaPO2H2)
Sodium hypophosphite CAS No. 7681-53-0 (NaPO2H2) is a colorless flaky crystal. The crystallization obtained from its aqueous solution is a hydrate (NaH2PO2·H2O), which is a monoclinic prism, colorless, easily deliquescent, readily soluble in water and alcohol, but insoluble in ether. It is relatively stable when stored in a dry state but decomposes when heated above 200℃. H2PO2- has a distorted tetrahedral configuration. Pure H3PO2 is a white crystal with a melting point of 299.7K, and it easily becomes a viscous liquid when supercooled. It is a monobasic acid with pKa=1.1 (293~298K). H3PO2 is a strong reducing agent, and its aqueous solution is not easily oxidized by oxygen in the air. Relatively, dilute solutions (mass fraction less than 20%) are more likely to be oxidized to H3PO3. At 413K, H2PO2 decomposes into H3PO4, PH3, and H2; in alkaline solution, it decomposes into HPO32- and H2, with the decomposition rate accelerating with the increase in OH- concentration.
Application of Sodium Hypophosphite (NaPO2H2) in Chemical Plating
Sodium hypophosphite CAS No. 7681-53-0 (NaPO2H2) is mainly used as a reducing agent in electroless nickel plating. The electroless nickel plating layer has many advantages in terms of smoothness, corrosion resistance, mechanical properties, electrical conductivity, magnetic properties, and so on, and it has been widely used in various industries. Electroless plating can also handle plated parts that electroplating cannot, such as holes, grooves, irregular surfaces, and larger plated parts. Other reducing agents used in electroless plating can be formaldehyde, sodium borohydride, hydrazine, dimethylamine borane, and low-valence metal ions. Using sodium hypophosphite CAS No. 7681-53-0 (NaPO2H2) as a reducing agent has the advantages of low redox potential, stable plating solution, and low cost, making it the most widely used.
Plating solutions using formaldehyde are unstable, and formaldehyde is toxic and pollutes the environment. Sodium borohydride decomposes easily in non-strong alkaline solutions, so the pH of the plating solution should be maintained above 11. Using hydrazine as a reducing agent, although there is no problem with harmful oxide accumulation and a high-purity nickel layer can be obtained, the plating layer has high internal stress and brittleness. Dimethylamine borane can operate over a wide pH range, but it is relatively expensive. Using low-valence ions (such as Ti3+, Sn2+, etc.) as reducing agents has the disadvantage that the redox reaction does not occur on the catalyst surface.
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