Reasons for Applying Multiple Layers of Paint

Key Points Note 

Following the basic painting process, a typically three-layer coating is applied. These three layers are known as the primer, intermediate coat, and topcoat, each playing a specific role in achieving the painting’s objectives as a team. 

1. Basic Steps of Coating 

The basic coating process involves coating with a multi-layer film consisting of three layers: primer, intermediate coat, and topcoat. The thickness of the multi-layer film is at most 0.1mm (100µm, about two sheets of newspaper), and even what is considered a “thick coating” like zinc-rich paint for heavy corrosion protection is only about three times that thickness (approximately 250 µm according to C-5 coating specifications). This is because achieving various painting purposes with a single-layer film is difficult, so it is accomplished through the cooperation of multiple layers. In traditional lacquer painting, once the base is prepared, three layers—primer, intermediate coat, and topcoat—are applied. These layers work together as a coating team and serve various functions. The general roles of each layer in painting.

2. What is a Coating System?

A combination of multiple layers of paint is referred to as a “coating system.” It needs to adhere firmly to the substrate, ensure good adhesion between each layer, meet mechanical strength and chemical resistance requirements, and adjust the appearance to meet specifications. Japanese paint technicians have tackled these challenges and established modern techniques. Typically, the name of the topcoat paint is included in the designation of a coating system. For example, in the case of JASS 18, it is labeled as “Process of constant-drying fluororesin enamel paint on iron surface.” In this case, a 2-component epoxy resin primer is used for the undercoat. JASS 18 is the standard specification for painting work established by the Japan Architectural Society. 

 

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