In painting operations, spray methods are primarily divided into three types: air spray, airless spray, and electrostatic spray. These methods increase coating efficiency in this order.
1. Air Spray Method
In this method, paint and pressurized air are mixed and atomized. The size of the mist particles depends on the volume ratio of air to paint, with a higher air ratio resulting in finer particles and a better finish.
The spray guns used have a central air hole, auxiliary air holes, and side air holes (corner holes) in the air cap. The air from the central hole, being the main airflow, reaches near sonic speeds at the nozzle exit, atomizing the paint to form a circular pattern. The side air holes flatten the spray pattern from circular to oval, with the direction of the corner holes determining whether the pattern is horizontally or vertically oval.
2. Airless Spray Method
Since the paint itself is pressurized, high-viscosity paints can be applied. The high pressure, typically around 10-30 MPa, causes the paint particles to be ejected like bullets, colliding with external air and atomizing onto the surface. This high pressure can penetrate human skin, so caution must be exercised to never direct it at people.
Compared to air spray, airless spray has less particle scatter and allows for thicker coatings, making it suitable for heavy-duty corrosion protection applications.