During blasting, the abrasive is shot at a fairly high velocity and strikes the surface of the steel substrate, not so high of course that the abrasive breaks prematurely before the metal is properly cleaned. Under high compressed air pressure, it will lead to excessive crushing and loss of non-metallic abrasives, so abrasives such as brown corundum should not use too high air pressure. During sandblasting, for softer or thin-walled substrates, low wind pressure and slightly finer sand should be used to reduce the possibility of sand embedding. For pressure sandblasting equipment, high wind pressure gas will generate large compressive stress. Using higher nozzle pressure will lead to deformation of the substrate of thin parts, and it is easy to increase the crushing rate of abrasives and increase the loss of abrasives. Table 7-9 lists the sandblasting production that can be obtained for different surface conditions by using a pressure-type sandblasting equipment with an air pressure of o.?MPa and a nozzle of a given diameter. Ability test results. In order to obtain the desired blasted surface, a visual inspection of the structure and uniformity of the blasted surface is required to determine the required blasting time. Excessive blasting times can lead to undesired surface structures.

After the steel substrate is sandblasted, the surface is clean and highly active and absorbs moisture. Therefore, the surface of the steel components after sandblasting should never be touched by hand. For touching and handling, wear clean gloves. The surface reaction ability of the steel substrate that has just been sandblasted is very strong. If the ambient temperature rises and the temperature of the workpiece is lower than the ambient temperature, condensation will occur on the surface of the workpiece and rust will occur. This kind of situation often occurs when anti-corrosion construction is carried out in northern my country, especially when some storage tanks are constructed. In autumn, due to the large temperature difference between day and night, this also happens during night construction. When using pressure sandblasting, the long-term operation of the air compressor increases the temperature of the compressed air, and the temperature is higher than that: the compressed air of the workpiece is easy to condense water droplets on the surface of the workpiece. This phenomenon can be avoided by using the centrifugal sand blasting process.

The surface of the steel components after sandblasting should be sprayed with metal coating as soon as possible. The shorter the interval between sandblasting and spraying, the higher the bonding strength of the coating. After the steel substrate is sandblasted, the atomic layer on the surface undergoes severe plastic deformation, the lattice defects increase, and the surface activity and adsorption increase. After the surface of the workpiece substrate is sandblasted, the surface activity is significantly improved, and low-energy electrons can be emitted at room temperature. The measurement of low-energy electrons can quantitatively describe the activation degree of the surface. With the prolonged storage time, the energy and quantity of low-energy electrons on the surface of the substrate will gradually decay, and the surface activity will decrease, which will affect the bonding strength of the thermal spray coating.