The earliest application of electrophoretic coating technology was primarily for industrial and automotive areas as a primer for subsequent painting.
However during the early 80’s development in resin technology enabled the application onto more aesthetic and decorative articles.
The early 80’s saw the utilisation of the E-coat process onto electroplated components for protection and tarnish resistance on, say, brass plating for example. Later developments of incorporating solvent soluble dyes provided finishes of gold onto nickel plating.
From there the process has evolved to where it is now – widely used around the world for a multiplicity of applications.
An E-coat paint solution consists of an emulsified polymer system in de-ionised water. When a D.C. voltage is applied to the tank through a positive (anode) and negative (cathode) electrode, electrolysis occurs where hydrogen is produced at the cathode and oxygen is produced at the anode. There is a simultaneous pH change which in turn results in a controlled precipitation of the polymer onto the appropriate electrode. The deposition electrode can either be the cathode or anode depending on the E-coat technology being utilised.
The very earliest commercialisation of this technology in the 1960’s involved anodic technology, where the part to be coated is made the anode. In this case the pH of the coating bath is slightly alkaline. One major disadvantage of anodic coating is that because oxygen is formed at the anode during deposition, certain substrates may be attacked. In fact, anodic coating is aggressive to the substrate. It is therefore not possible to coat brass, silver and to some degree zinc parts anodically because the appearance of the metal is adversely affected.
However, anodic coating is still widely employed for application onto aluminium extrusion alloys and castings, stainless steel and phosphated steel.
Cathodic deposition takes place in acid bath conditions and depending on the formulation can be anything between 4-6 pH. Because of its passive deposition the cathodic process does not affect the metal surface, making it by far the most versatile method of application.
Due to the nature of the E-coat method of application there are a number of significant advantages over conventional coating processes. The two main advantages are that firstly, it is possible to apply a conformal coating to complex shapes, secondly, the coating can be applied at a controlled and even film thickness. A further important advantage is that the process time is significantly less than other metal finishing methods such as anodizing and electroplating. In addition, it is a much more environmentally friendly, eco-conscious, water based technology.
The equipment required for E-coat metal finishing is relatively simple and low cost which enables the customer to produce large, fully automated coating lines at a fraction of the cost of complicated, state of the art spray coating systems.
There are numerous benefits of the E-coat process which include:-
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