Plating processes have been used for hundreds of years to help strengthen metal against corrosion and wear as well as to add aesthetic flair to an otherwise dull appearance. Various plating methods employ either electric or chemical methods of dispersing a thin layer of metal coating on a metal substrate. Electric processes use a slight metal current in a chemical bath. As the electricity passes through a wire onto the substrate, the oxidation process disperses metal flakes and salts in an even layer coating. Electroless processes simply employ a chemical reaction to produce similar, stable results.
The Invention of Plating
The actual development of plating began in the early 1800s when electrochemical piles were developed that could pump current through wires. This innovation found little application initially, but in 1837 G. Bird described electrodeposition of nickel chloride or sulphate on platinum. This process resulted in a thin crust of nickel on the platinum substrate, and soon after other European experiments proved nickel chloride, nitrate and nickel ammonium sulphate were also appropriate for nickel plating processes. The nickel ammonium sulphate, or double nickel salts, solution became industry standard for the next seventy years in commercial products.
Dr I. Adams of the United States patented a nickel ammonium sulphate bath in 1869. His main contribution to the process, and one for which he was much chastised by rivals, was that the electrolytic bath should be neutral and “free from the presence of potash, soda, alumina, lime or nitric acid, or from any acid or alkaline reaction.” Dr. Adams engaged in an aggressive marketing campaign for his solution in the United States and Europe, resulting in a near universal acceptance by industrial countries. Experimentation and innovation continued by Adams’s rivals, who attempted to incorporate nickel sulphate, and citric or benzoic acids to the electrolytic bath in an attempt to develop alternate plating processes. Some of these caught on while others garnered small to no followings.
In 1916, Professor O.P. Watts published a formula in the United States for a bath that is still in use with few changes. His basic formula is:
Nickel sulphate, NiSO4 • 7H2O 240g/l
Nickel chloride, NiCl2 • 6H2O 20g/l
Boric acid, H3BO3 20g/l
Temperature and air agitation levels varied in the UK and the USA for quite some time until international standards were developed in the 1930s. These standards included raising the bath’s temperature from the previously used room temperature and introducing air agitation shake up of the bath itself.
The Watts formula has undergone a few changes to introduce new capabilities in nickel plating, such as the change in the composition to produce “bright” nickel plating, which has more luster than a standard nickel plating. Additionally, a chemical composition was developed to provide for electroless nickel plating, which does not require a steady source of power to produce a current and is therefore cheaper. Both electric and electroless nickel plating are widely used processed around the world for metal coating deposition.
Ancient Plating Theories
Plating processes might have been used in ancient times if theories about the "Parthian Batteries” are correct, but more recent and still-current methods were developed and improved upon throughout the 19th century. These changes were the product of experimentations with chemical composition of the baths used to plate as well as new methods for isolating metals and chemicals from one another. Currently, plating processes are so well-refined that they can be performed by large industrial concerns down to the home hobbyist in a garage.
There is some evidence that certain artifacts in ancient Mesopotamia could have represented an electrochemical battery that some historians believe could have been used to electroplate gold onto jewelry and other desirable objects. Modern experiments prove that if the Mesopotamians knew how to properly wire the artifacts, the electrochemical current from a simple lemon could have performed the job. But the theories espousing this view are suspect at best, although not impossible.