I would like to know the similarities and differences between shot blasting and sandblasting for rust removal

They’re different, right? The particle sizes vary, and their uses are also different; it seems that shot blasting is used to relieve stress, while sandblasting is used for rust removal

1. What is the process of shot blasting? Shot blasting is a method of removing rust from metal by using metal pellets, with compressed air or mechanical centrifugal force as well as friction serving as the driving forces. The pellet diameter ranges from 0.2 to 2.5 mm, the compressed air pressure is 0.2 to 0.6 Mpa, and the angle between the jet and the surface is around 30 degrees to 90 degrees. The nozzles are made of T7 or T8 tool steel and quenched to a hardness of 50-55HRC; each nozzle has a service life of 15-20 days. II. What is its use? Shot blasting is used to remove scale, rust, molding sand, and old paint from medium and large metal products as well as cast and forged parts with a thickness of at least 2 mm, or those for which precise dimensions and contours are not required. It is a cleaning method prior to surface coating. It is widely used in large shipyards, heavy machinery factories, automobile factories, etc. Note: Although sandblasting is also a mechanical cleaning method, it is not the same as shot blasting. Sandblasting uses particles such as quartz sand, while shot blasting uses metal pellets. With the increasing emphasis on environmental protection and industrial hygiene, sandblasting has been largely replaced by shot blasting, as the process generates large amounts of dust that not only severely pollutes the environment but also easily causes occupational diseases in operators (silicosis).

Shot blasting cannot eliminate stress; the best way to do so is through heat treatment. Ultrasonic treatment can also be used in cases where strict requirements are not applicable

Castings are generally subjected to shot blasting or sandblasting, commonly referred to as shot blast and shot penning. Shot blasting is efficient, but it can result in dead zones, while sandblasting is more flexible yet requires more energy. Sandblasting uses high-pressure air as a power source, while shot blasting relies on a high-speed rotating flywheel to propel steel shots at high velocity. The surface quality of castings produced by shot blasting is not as good as that achieved through sandblasting, but it is more cost-effective. Moreover, it can remove some of the sand adhering to castings that is difficult to clean away, whereas sandblasting cannot do this. Sandblasting and shot blasting are two different surface hardening processes; the hardness achieved through sandblasting is lower than that obtained through shot blasting, and different tools are used for each process! Sandblasting and shot blasting differ mainly in the type of medium used for spraying; naturally, their effects also vary. Sandblasting is more precise, making it easier to control accuracy and surface flatness. Shot blasting is more cost-effective and practical, as it’s easier to manage efficiency and costs, and the diameter of the steel shots can be controlled to adjust the spraying effect. 1. Both shot blasting and sandblasting are surface treatment methods, but it’s not true that only castings are treated using shot blasting. 2. The main function of sandblasting is to remove rust and oxide layers from surfaces, such as those of parts after heat treatment. Shot blasting, on the other hand, has a wider range of functions: it not only removes rust and oxide layers but also increases surface roughness, eliminates machining burrs, reduces internal stresses in parts, minimizes deformation after heat treatment, and improves the wear resistance and compressive strength of the surface. 3. There are many applications for shot blasting, including treating castings, forgings, and parts after machining, as well as parts after heat treatment. 4. Sandblasting is typically carried out manually, while shot blasting is often done in automated or semi-automated ways. 5. The steel shots and iron shots used in shot blasting aren’t really “shots” in the true sense; they are actually small wires or rods that appear like shots after being used for some time. As for the sand used in sandblasting, it’s simply river sand, similar to that used in construction, though it’s screened to have less mud and uniform particle sizes. Of course, there are differences in various industries as well. For example, in the shipbuilding industry, real steel balls are used for shot blasting, while metal ore sand (not river sand or quartz sand) is used for the same purpose. Balls are generally spherical particles without any edges or corners, such as wire cut balls and steel balls; sand, on the other hand, refers to granules with edges and corners, such as brown corundum, white corundum, and river sand. Spraying and throwing: Spraying uses compressed air as a driving force to propel sand or pellets onto the surface of a material, thereby removing debris and creating a certain level of roughness. Throwing is a method that uses the centrifugal force generated by high-speed rotation of the pellets to impact the surface of the material, thereby achieving cleaning and a certain level of roughness.

Sandblasting is a manual rust removal method in which a high-powered air compressor is used to remove rust from the metal surface, achieving a maximum surface roughness of level 2.5. Shot blasting is a mechanical rust removal method, but its resulting roughness is higher than that of sandblasting.

The size of the particles and all the materials vary, right? Shot blasting can help to reduce stress to a certain extent; the working environment for shot blasting is relatively good, while sandblasting creates a dusty environment that is less favorable.

Does that colleague have any quality standards for rust removal? How are levels classified? Please share it! Thank you!

Another difference is that shot blasting can eliminate various types of stresses such as casting stresses and welding stresses, while sandblasting merely removes surface oxides and the like

In terms of shape, the pellets are round while the sand has an irregular polyhedral form. Therefore, it is better to talk only about the roughness achieved by sandblasting; the effect of shot blasting is not as good as that.

It is not because the sandblasting process generates large amounts of dust that causes severe environmental pollution and harm to human health, that shot blasting is used as a substitute for sandblasting. This statement is incorrect. Dust is generated because sand has low hardness and low specific gravity, and it also contains a high amount of soil (such as river sand), which is why large amounts of dust end up contaminating the environment ； The cause of silicosis, which poses harm to the human body, is the presence of large amounts of free silicon in the sand (such as quartz, granite, yellow sand, etc.). Therefore, when these problems arise, it’s not sufficient to use shot blasting as a substitute for sandblasting; instead, it is necessary to use sand that is clean, has little dust, and does not contain free silicon for sandblasting. After all, the cost of shot blasting is high, so most people opt for sandblasting due to its lower cost while still achieving the same results. Garnet abrasives are used for sandblasting large containers and storage tanks, steel structures, pipelines, drilling platforms, as well as carbon steel and stainless steel components in the shipbuilding industry. They help to completely remove rust, soluble salts, and other contaminants. The surfaces treated by sandblasting have no embedded particles, nor any undesirable protrusions or pits, allowing for a SA3 white metal finish. The surface roughness can range from 50–75 microns to 60–95 microns. Due to its excellent toughness and low brittleness, it can be reused up to 6-10 times, depending on the specific application. It contains no free silicon, heavy metals, or toxic substances, and meets occupational health and safety requirements. The chloride content is 10-15 ppm, meeting the strictest industrial and military technical requirements. After 6 washes, the dust content is extremely low, which **improves the working environment** during sandblasting.