Metal plating processes are associated with creating outer coatings of chromium, copper, nickel and other metals in order to prevent corrosion or in order to enhance the visual appeal of a parent metal. Electroplating techniques typically involve immersing a metal into an acid solution using a cathode and anode electric current. The material that will be plated is known as the cathode which is a negative electrode whereby a direct type of electric current will pass through.
The bath or the solution consists of the needed metal in an oxidized form which will be an aquated cation or complex ion. The anode will typically be the metal bar that will be plated. During an electrolysis process, the metal will deposit onto the work and then the metal on a bar will dissolve. This entire process has been governed by what is known as the Faraday’s law of electrolysis.
The Uses Of Electroplating
- Mechanical or engineering properties
- Specialized surface properties
- For decoration or appearance
The Components Of Metal Plating Processes
Metal surface and cleaning preparation:
- Alkaline cleaning
- The process related to “oxide removal”
- Electroless-plating which is described as autocatalytic
Protection and the finishing treatments
- Chromate conversion
- Anodizing and phosphating
The General Steps In The Electroplating Process
- Step One- Cleaning the surface will be necessary in order for bonding to occur
- Step Two- Rinsing and then drying if necessary
- Step Three- Etching and acid cleaning
- Step Four- Rinsing if required
- Step Five- Plating or conversion coating
- Step Six- Water rinsing
- Step Seven- Chemical rinsing in order to ensure the parts become more rust-resistant
- Step Eight- Rinse the parts in very hot water
Electroplating is a process that makes use of electrical currents to drive specific chemical reactions in the process of reducing the metal ions.
The autocatalytic process can be described as a type of chemical reaction that induces a metal atom reduction. This process uses substrates that are non-conductive and the process requires no electricity. The plating parameters can be difficult as well as the plating bath that has a limited lifetime.
This process is known as conversion coating and a few examples of this include:
- Black oxide
- Iridite on aluminum
Conversion coating processes add a dimensional type of growth to the thickness. However, it will not create direct relationships as this process will consume a percentage of substrates metals.
In these processes, metal ions are reduced from the solution during the exchange process that occurs between a metal atom that was derived from a substrate. The deposited metal will have to have a higher Electromotive Force compared to the dissolved metal.
- Surface Protection that also is known as sacrificial coatings or anodic coatings is used to protect what is known as a base metal and is mainly used for steel and iron.
- Decorative Coatings which offer a slight protection level and make these metals appear more attractive.
- Engineering Coatings are used to impart particular properties onto a surface. Some examples will include surfaces that will increase reflectivity, conductivity, and solderability.