Electroless nickel plating (also known as electroless nickel plating or autocatalytic nickel plating) is a technique for depositing a nickel layer on a metal surface in the absence of an applied current. The process is based on a chemical reduction reaction in which metallic nickel ions are reduced to metallic nickel by a reducing agent in solution and deposited on the surface of the workpiece.
Author: Anna
Electroless nickel plating (also known as electroless nickel plating or autocatalytic nickel plating) is a technique for depositing a nickel layer on a metal surface in the absence of an applied current. The process is based on a chemical reduction reaction in which metallic nickel ions are reduced to metallic nickel by a reducing agent in solution and deposited on the surface of the workpiece.
The basic principle of chemical nickel plating involves the following key components:
Metal salts: Usually nickel salts, such as nickel sulfate, nickel chloride or nickel acetate, which provide the nickel ions needed for deposition.
Reducing agents: Responsible for reducing the nickel ions to nickel metal, common reducing agents include sodium hypophosphite (NaH2PO2), formaldehyde (HCHO), hydrazine (N2H4), and borohydrides (e.g., NaBH4).
Buffer or pH adjuster: maintain the pH value of the plating solution in a suitable range to ensure the stability of the chemical reaction. Commonly used buffers include ammonia, triethanolamine, etc.
Stabilizers or complexing agents: help to control the stability of the plating solution and the activity of nickel ions to ensure the deposition rate and the quality of the coating. For example, citrate can be used as a complexing agent.
The reaction mechanism of chemical nickel plating is as follows:
A reducing agent (e.g., sodium hypophosphite) decomposes on a catalytic surface (usually a metal substrate or a pre-deposited layer of catalytic metal) to produce an active hydride.
The active hydride reduces the nickel ions in solution to nickel in the metallic state, which is deposited on the surface of the substrate.
At the same time, the reducing agent itself is oxidized, e.g., hypophosphite ions are oxidized to phosphite ions.
Possible by-products of the reaction include hydrogen gas and water.
An important feature of electroless nickel plating is that it can be deposited on complexly shaped workpieces and on non-conductive surfaces, which is not possible with conventional plating techniques. In addition, chemical nickel plating layers usually have good uniformity, hardness and corrosion resistance, and are therefore widely used in many industrial fields.