Dip coaters take finished products - usually made of metal - and submerge them, or dip them, in molten plastic in order to achieve a thin protective coating on the surface. The process of dip coating is simple, quick and relatively inexpensive, and is used widely in a number of industries.
Dip coaters use a three step process. First, the product is cleaned and prepared for dipping. Objects are sometimes coated with chromate or phosphate to increase adhesion between the object's surface and the molten plastic. The product is then dipped into the molten plastic and allowed to sit there for a specific time. The longer an object is submerged in the plastic, the thicker the coating will be. Lastly, the object is removed slowly from the molten material and allowed to dry. Removal speed has to be slow and constant to prevent surface irregularities due to different thicknesses. Objects can be dried and hardened in a heat chamber to ensure fusion between the surface and the coating. Every day objects such as tool handles, fitness and sports equipment, and playground equipment have been dip coated in a melted plastic. The most common material choices for plastic coating are PVC (polyvinyl carbonate) and plastisol which is another form of vinyl.
The purpose of using dip coating is both decorative and protective. Plastic can be manufactured in many different colors, and can be finished according to a desired texture making the decorative capabilities of dip coating very broad. Covering the handles of many everyday objects also improves the comfort and grip for those using the items. However the more important reason for using dip coating is for its protective and insulative properties. Electrical wires and connectors and products such as jumper cables and plastic closures are covered by dip molding in order to provide thermal and electrical insulation. Wire fences and other products intended for outside use are plastic coated to protect against corrosion. Further advantages of dip coating include the low labor costs due to the process being almost fully automated. As plastic tends to dry and harden quickly, dip coating can have a high volume turnover in a relatively short time which allows for large batches of products to be dipcoated. Dip coating is not limited by object size or dimension as the container of molten plastic can be adjusted according to dipping needs. For objects such as wire which typically is manufactured in long lengths, a continuous motion dip molding can be used, ensuring total coverage of the surface.