Electroless nickel plating also known as nickel electro-deposition, is becoming an increasingly popular process for a variety of different manufacturing applications. Electro nickel plating is a process that uses an electrical current to coat a conductive material, typically made of metal, with a thin layer of nickel. Other metals used for electroplating include stainless steel, copper, zinc, and platinum.
Benefits of Electro Nickel Plating
In general, electroless nickel plating improves a wide range of characteristics not inherently present in the base material. Some of these benefits include:
- Increased resistance to corrosion
- Improved hardness
- Superior strength
- Resistance to wear
- Improved ductility
How Electroless Nickel Plating Works
To transfer nickel onto the surface of a product properly, a negative charge must be applied to the base material. To achieve this, the product is typically attached to a rectifier, battery or other power supply via a conductive wire. Once attached, a rod made of nickel is connected in a similar fashion to the positive side of the rectifier or power source. Once the initial steps have been completed, the base material is submerged in a solution that features a salt with a chemical makeup, including the electroplating metal. With electro nickel plating, this solution consists of water and nickel chloride salt. Due to the electric current present in the solution, the nickel chloride salt dissociates to negative chloride ions and positive nickel cat-ions. The negative charge of the base metal then attracts the positive nickel ions, while the positive charge of the nickel rod attracts the negative chloride anions. Through this chemical reaction, the nickel in the rod oxidizes and dissolves into the solution. From here, the oxidized nickel is attracted to the base material, and subsequently coats the product.
Current Density in the Electroless Nickel Plating Process
Electro nickel plating involves a wide range of current density levels. Current density directly determines the deposition rate of nickel to the base material—specifically, the higher the current density, the quicker the deposition rate. Current density, however, also affects plating adherence and plating quality, with higher current density levels delivering poorer results. Therefore, the optimal level of current density depends on the type of base material and specific type of results the final product requires.
One way to avoid working at lower current densities is by employing a discontinuous direct current to the electroplating solution. By allowing between one and three seconds of break time between every eight to fifteen seconds of electrical current, high current densities can produce a higher level of quality. A discontinuous current is also beneficial for avoiding over-plating of specific sections on the base material. Another solution to the current density issue involves incorporating a strike layer to the initial electro nickel plating process.