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Applications of Electroless Nickel Plating

Electro 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, electroplating 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

Nickel is considered useful for electroplating metal because it provides superior ductility, corrosion resistance, and hardness. Electro nickel plating can also improve a product’s brightness and external appearance. Different nickel-plating chemicals incorporated into the process deliver anything from a semi-bright and fully bright cosmetic effect, to matte, pearl, or satin finishes.

How Electro 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 Electro 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.

Strike Electro Nickel Plating

Another solution to the current density issue involves incorporating a strike layer to the initial electro nickel plating process. A strike layer, also known as a flash layer, adheres a thin layer of high-quality nickel plating to the base material. Once up to 0.1 micrometers of nickel coats the product, a lower quality current density is used to improve the speed of product completion. When different metals require plating to the product’s base material, striking can be used. In cases where nickel serves as a poor adherent to the base material, for example, copper can be a buffer prior to the electro nickel-plating process.

Pre-treatment Process for Electro Nickel Plating

Proper pre- and post-treatment of the base product has a direct correlation to the quality and deposition rate of electro nickel plating. To help ensure uniform and quality adhesion, chemical or  manual preparation includes the following three steps:

  • Pre-treatment surface cleaning: Surface cleaning entails eliminating contaminants through the use of solvents, abrasive materials, alkaline cleaners, acid etch, water, or a combination thereof.
  • Surface modification: Modifying the exterior of the base product improves adhesion through processes such as striking or metal hardening.
  • Post-treatment surface cleaning: Performing fin ishing operations, such as rinsing, end the electroplating process.

Once pre-treatment cleaning is complete, testing the level of cleanliness in the base material prior to beginning the electro nickel plating process is a good idea. To do this, the waterbreak test is recommended. In this test, the treated substrate is rinsed and held vertical. If contaminants such as oils are absent, then a thin sheet of water remains unbroken across the entire surface of the base material.

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