1. Fully understand the performance of the coating before using it
Different paints have different viscosity changes during the heating process. Some viscosity changes greatly after the temperature rises, while others do not. For example, oil-based paints, after the temperature rises, the viscosity decreases a lot. For water-based paints, heating has little effect on its viscosity. Two-component paint has a very short shelf life after mixing, and heating it will further shorten its service life, so two-component paints and water-based paints with poor thermal stability generally cannot be sprayed with heat. The physical and chemical properties of some paint components will change during the heating process, even discoloration, so it is necessary to fully understand the performance of the paint in advance.
2. Understand the performance of solvents in coatings
If the solvent used in the paint has a very low boiling point, it will evaporate too quickly during thermal spraying, causing the paint film to be too dry or produce orange peel. In spraying with heated air, the temperature of the paint should not exceed the boiling point of the solvent with the lowest boiling point among the various solvents it contains, because the solvent will boil if it exceeds its boiling point, and intermittent spray will be generated at the nozzle of the Spray Gun, which will affect the spraying effect. . The boiling points of commonly used solvents are shown in Table 4-15. Therefore, special attention should be paid when the paint contains low boiling point solvents such as methylene chloride or acetone.
In the high-pressure airless heating spraying system, the temperature of the coating is usually raised above the minimum boiling point of the solvent contained, which not only can obtain better atomization effect, but also helps to control the viscosity of the coating and obtain good leveling. However, care should be taken to ensure that the physical and chemical properties of the coating do not change at this temperature.
3. Length of paint hose between heater and Spray Gun
The length of the paint hose between the heater and the Spray Gun should not be too long. In order to accurately control the temperature of the paint, the length of the paint hose between the heater and the Spray Gun should generally be controlled within 6m. If the process requires the use of longer paint hoses, use dedicated heated hoses.
4. Understand the problems that are prone to occur in thermal spraying
For example, the heater used for heating often requires more maintenance in order to ensure its normal operation. In order to ensure a constant coating temperature and consistent coating quality, a circulation system is usually used, and the feeding pump needs to run continuously. This will inevitably increase the loss of the pump and the operating cost. In order to circulate the paint, two paint hoses must be connected to the Spray Gun, which not only increases the weight of the Spray Gun, but also increases the difficulty and burden of holding the Spray Gun.
