What is the surface pretreatment of thermal spraying?

       Today, the metal spraying manufacturer will mainly explain to you what is the surface pretreatment of thermal spraying!



The surface pretreatment of thermal spray processing is generally divided into three steps: surface pretreatment, surface purification and surface roughening (or activation).



1. Surface pretreatment:



1. Make the surface of the workpiece suitable for coating deposition and increase the bonding area;

2. It is beneficial to overcome the shrinkage stress of the coating. Some parts of the workpiece are pretreated to disperse the local stress of the coating and improve the shear strength of the coating. Common methods are fillet cutting and pre-coated grooves. Coarse threading of the workpiece surface is also one of the commonly used methods, especially when spraying large workpieces, turning threads are usually used to increase the bonding area.

2. Surface purification:



Solvent cleaning, alkaline cleaning and thermal degreasing are commonly used to remove oil from surfaces and keep them clean. Commonly used cleaning solvents are gasoline, acetone, carbon tetrachloride and trichlorohexane. Alkaline cleaning is often used for large repair workpieces. Lye is usually prepared with sodium hydroxide or sodium carbonate, which is a cheaper method.



3. Sandblasting and roughening treatment: (This is an important pretreatment method for thermal spraying.)



Sandblasting can form a uniform, uneven rough surface on the cleaned surface, which is conducive to the mechanical bonding of the coating. Using clean compressed air to drive clean sand to the surface of the workpiece will generate compressive stress on the surface of the substrate, remove the surface oxide film, and cause some surface metal lattice distortion, which is conducive to the physical bonding of the coating. Base metal blasting for clean, rough and highly reactive surfaces