Shop primer, also known as maintenance primer or pretreatment primer, is a layer of antirust paint sprayed on the assembly line after steel plate or section steel has been pretreated by shot blasting to remove rust. The function of the shop primer is to protect the surface of the shot blasted steel and prevent corrosion damage caused by the rust of the steel during processing and ship construction.
A shop primer is a coating that is applied immediately after the steel plate has been derusted. The steel plate must first be processed . Firstly, the moisture, sludge and loose scale on the steel plate are removed by blowing, heating or fixed wire brush to remove floating rust, and then a dry and clean surface is obtained. Then throw steel shot or steel wire on the surface of the steel plate to remove the rust and scale, and it will show the natural color of the metal. Generally, it needs to reach the Swedish standard Sa2.5 level, and the inorganic zinc-rich primer for special requirements must reach the Sa3 level. . The roughness of the steel plate is related to the type of abrasive used in shot blasting , and the roughness needs to be appropriate. Generally, the thickness of the steel plate is 40~70, and that of the thin steel plate is 25~35; the roughness of the inorganic zinc-rich primer should not be too small, so as to ensure the paint film Adhesion on steel plates .
Immediately after removing the dust, use an automatic high-pressure Spray Gun to spray the shop primer , and then heat and dry in a certain length of oven, so that when the steel plate leaves the assembly line roller, it has reached the dryness that can be sucked and stacked. degree. The design of the assembly line requires that the shop primer is generally dried for three minutes. Slow drying will cause damage to the paint film when the shop primer moves on the raceway or is sucked and lifted. However, it should not be dried too fast, which will cause the paint mist to leave the nozzle of the Spray Gun and be partially dry before reaching the surface of the steel, forming a loose and discontinuous paint film, which will affect the protection of the steel. Therefore, the two-component (or three- component ; to control the viscosity of the paint, the suitable viscosity is about 15~20s (-(paint-4 cups) Solvents, such as toluene, acetone, isopropanol, etc., the amount of diluent added is 0~15%. Pay attention to the nozzle diameter and pressure of high-pressure airless spraying and the moving , and strictly control the thickness of the coating film. Airless The nozzle number for spraying is "0.017~0.023"; the painting pressure is 10~15MPa"; it has the shortest painting interval time limit, and the general repainting should be after 16 hours. The second can of paint should be finished within a certain period of time after deployment. When the machine is used up, all pipes and high-pressure pumps should be cleaned up when the machine is shut down.
