Plating is the process of covering the surface of a material or workpiece with a different metal. Plating provides a number of useful benefits, such as inhibiting corrosion, changing conductibility, improving wear, boosting solderability, reducing friction, heat resistance, and hardening the material. Plating can change the qualities and the performance of the material, which changes its uses in precision machining. Here we examine the different types of plating and how they affect the material, with an inside look at how these processes affect precision machining.
Electroplating is the most common method of plating. Electroplating uses an electrical current to dissolve positively charged metal particles (ions) in a chemical solution. The positively charged metal ions are attracted to the material to be plated, which is the negatively charged side of the circuit. The part or product to be plated is then placed in this solution, and the dissolved metal particles are drawn to the surface of the material. Electroplating results in a smooth, even and rapid coating for the material that is plated, effectively changing the surface of the material. There are a number of different steps and processes that can be involved in electroplating, including cleaning, striking, electrochemical deposition, pulse electroplating, and brush electroplating.
Electroplating is used to provide a protective coating, a decorative appearance, or to change the properties of a material for engineering. Electroplating improves the chemical, physical, and mechanical properties of the workpiece which affects the way it performs when machined. Plating the workpiece can be used to build it up from a smaller size, make it easier to machine, and to increase solderability, conductivity or reflectivity.
ELECTROLESS (AUTOCATALYTIC) PLATING
Electroless plating is so called because it is a plating method that does not use external electric power. Electroless plating involves a chemical reaction that induces metal atom reduction. In other words, the solution of metal ions (particles) when mixed with a reducing agent is converted into a metal solid when they come in contact with the catalyzing metal (which triggers the reaction). This results in the metal being plated with a solid layer of the plating metal.
ELECTROLESS PLATING EFFECTS
Electroless or autocatalytic plating is suitable for diverse sizes and shapes of materials and doesn’t require external electricity or plating baths, which reduces costs. However, electroless plating is slower, can’t create thick plates, and is more difficult to control than electroplating. The most common method of autocatalytic plating is electroless nickel plating. However, plating in silver, gold, and copper can also be applied with this technique.
Effects of electroless plating on the end product include protecting the base metal from corrosion, increasing the size of the workpiece, and altering solderability, reflectivity, and conductivity.
Immersion plating involves immersing one metal into a solution of metal ions from a more noble metal. The ions from the nobler metal are more stable, and so there is a natural ‘pull’ to displace the surface metal ions from the less noble metal with a thin layer of the nobler metal ions. Immersion plating is a slower process, and can only be used for plating less noble metals with nobler metals. Nobler metals are metals that are chemically inert. For example gold, platinum, or silver.
IMMERSION PLATING EFFECTS
Immersion plating results in only a thin coverage of plating, after which point the plating process will stop. Immersion plating also seems to be of poorer adhesion quality, where the plating doesn’t ‘stick’ as firmly to the base metal.
The effects of immersion plating on the end product include improved corrosion resistance, altered electrical conductivity, changed appearance, greater hardness, torque tolerance and modified bonding capabilities.
Metal plating can alter the properties of the material for applications in precision machining and change the qualities of the end product. Understanding the impact of plating on your workpieces means evaluating the benefits and drawbacks of plating and how plating impacts machining. Talk to your precision machining provider about how plating will impact your workpieces and whether it’s the right choice for your project.