Mechanism of sodium hypophosphate in nickel plating

The mechanism of sodium hypophosphate,SHPP,CAS:10039-56-2 (NaH2PO2 .H2O) in chemical nickel plating is very complex, involving multiple chemical reactions and processes. Here is a more detailed explanation:

1. Reductant action

Sodium hypohosphate is the most commonly used reducing agent in chemical nickel plating and its main function is to reduce nickel ion (Ni²) to metal nickel (Ni). This process can be represented by the following reaction form:

Ni2+2H2PO2+2H2O-->Ni+2H2PO3-+2H+H2

In this reaction, sodium hypophosphate provides electrons to reduce Ni² to Ni while oxidized itself to a phosphite.

2. Provide hydrogen ions

Sodium hypophosphate releases hydrogen ions (H) during decomposition, which helps maintain the acidic environment of the solution. The acidic environment is crucial for the reduction reaction of nickel ions because it prevents the premature hydrolysis of nickel ions to form nickel hydroxide (Ni (OH)2), thus ensuring that nickel ions can be effectively reduced to metal nickel.

3. Form a phosphate compound

During decomposition, sodium hypophosphate not only releases hydrogen ions, but also produces phosphorus, which co-deposits with nickel to form a nickel-phosphorus alloy (Ni-P). NP has excellent hardness and corrosion resistance, which makes chemical nickel plating very popular in many industrial applications. The content of phosphorus can be controlled by adjusting the concentration in the coating, thus adjusting the performance of the coating.

4. Stable plating solution

Sodium hypophosphate also plays a role in stabilizing plating during chemical nickel plating. It can prevent the premature reduction of nickel ions in the plating solution, thus avoiding the formation of nickel particles or precipitation in the plating solution. This helps to ensure the stability and uniformity of the coating.

5. Promote auto catalytic reactions

Chemical nickel plating is an auto-catalytic process, meaning that once the nickel begins to deposit on the substrate, the deposition process proceeds automatically and continuously. Sodium hypophosphate plays a key role in this process. It continues to reduce the nickel ions on the deposited nickel surface, continuous thickening of the coating.

6. Side effects

In the process of chemical nickel plating, sodium hypophosphate will also participate in some side reactions, which will produce hydrogen (H2). The formation and release of hydrogen bubbles will help to stir the plating solution and prevent the defects of the coating.

7. Effect of plating solution composition

Other components in the plating, such as complexers, buffers and stabilizers, also affect the action of sodium hypophosphate. Complexing agent (such as citric acid, lactic acid, etc.) can stabilize nickel ion and prevent their premature reduction; buffer (such as boric acid) can maintain the pH,stabilizer (such as lead ion) can inhibit the spontaneous decomposition of plating.

Sum up

Sodium hypohosphate,CAS:10039-56-2, plays multiple roles in chemical nickel plating, including serving as a reducing agent, providing hydrogen ions, forming phosphate, stabilizing plating and facilitating auto-catalytic reactions. Together, these effects ensure the smooth progress of the chemical nickel plating process, and the final formation of high quality, high performance nickel and phosphorus alloy coating.