The Electroplating Process?
What exactly is the Electroplating Process?
Possibly the most common of all questions asked when speaking to new clients, new employees or just a curious mind:
The answer that most simply describes the process can be found in its definition according to Oxford – Electroplating is a process in order to coat (a metal object) by electrolytic deposition with chromium, silver, or another metal.
This definition is a rather basic way of saying that electroplating is just the covering of one metal, with another. Simple, right?
Well, once we start introducing other terms and processes such as electrodeposition, electrochemical deposition, galvanic plating, electrophoretic deposition, underpotential deposition, electro metallisation, we can then start to see the real complexity and nuance within.
Electroplating is a surface modification that is governed or controlled by the chemistry of the plating solution and is driven or initiated by applied electrical energy. So, this means that electroplating requires a bath or tank of mixed chemicals (this controls / maintains the electrochemistry), and in order for any electroplating to take place, electrical current is needed to move the ions through the solution and onto the workpieces.
It involves the reduction of metal ions from a solution onto a conductive surface. When a direct current is applied across two electrodes immersed in an electrolyte solution, the electrode connected to the negative terminal of the power supply (usually a rectifier or even a car battery in some cases) becomes the cathode, which is the object to be plated.
The positive terminal is connected to the anode, typically composed of the plating metal or an inert conductor. Inert conductors are used when the metal being plated is suspended in the solution by means of a generation or dissolving tank and the actual metal to be plated is NOT connected to the anode buzz bar. This is useful when plating alloy metal coatings such as Zinc-Nickel Alloy.
In the electrolyte (or electroplating solution), metal cations (such as Cu²⁺, Ni²⁺, or Zn²⁺, or any other metal to be plated) exist in solution, stabilized by complexing agents or acids. These cations are attracted to the cathode, where they encounter a surplus of electrons delivered by the power source. When a metal ion reaches the cathode surface, it gains electrons in a reduction reaction and deposits as a neutral metal atom. For example, Cu²⁺ + 2e⁻ → Cu(s). This deposition forms a coherent, uniform metallic layer on the cathode surface.
Simultaneously, at the anode, oxidation occurs. If the anode is made of the plating metal, it dissolves into the solution as metal cations, replenishing the ions consumed at the cathode and maintaining the concentration of metal in the bath. This is expressed as M(s) → Mⁿ⁺ + ne⁻. If an inert anode is used, no metal is replenished and the electrolyte must be manually maintained by pouring the metal cations into the solution.
The rate and quality of deposition are influenced by the current density, ion concentration, temperature, agitation, and the electrochemical potential of the system. So, there are many elements to the plating solution to consider in order to maintain an effective plating process. On the atomic level, the process is driven by electrostatic forces, diffusion, and charge transfer kinetics. Over time, a thin and often (hopefully) uniform layer of the desired metal builds up on the substrate, effectively coating it for common purposes like corrosion resistance, aesthetic appeal, conductivity, or wear resistance.
Electroplating is also known as electrochemical deposition. This is due to the fact that the ‘coating’ is applied from within a chemical bath using electricity to attract the metal suspended in the solution onto the metal piece one would want to electroplate, just as we have explained. The anode being the metal suspended from the positively charged buzz bar (where the metal you wish to plate is suspended), and the cathode (negatively charged), being the workpieces one wishes to electroplate.
These are the basics of the electroplating process. There are many other terms to describe similar processes such as electrodeposition. According to wikipedia ‘Electrodeposition is an electrolytic process used to deposit a metal onto a substrate from a solution. It involves the reduction of metal cations at the cathode, resulting in a coherent metal coating’.
And it doesn’t stop there.
The other terms you hear floating around like: electro galvanising, galvanic plating, electro metallisation, cathodic plating and many other terms that have their own relevance.