In order to achieve the anti-corrosion effect of color coated board, at least three kinds of isolation coatings (Figure 1-1) should be applied on each chemical coating side of the substrate, which are chemical conversion coating, primer coating and top coating. In the early days, there were only two layers of color coated wires, that is, only one layer of chemical substrate conversion coating and one layer of bottom and surface coating. However, due to the poor anti-corrosion effect, the current color coated wires are usually coated with three or more layers, and some home appliance boards are even coated with four or five layers according to the actual needs. This is the reason why the color coating line described in the next few sections has a variety of technological processes, such as two coating and two drying, three coating and three drying, four coating and four drying. Generally speaking, the color coating line with more coating and more drying is generally used for printing color coated board production.