Detailed process of rust removal on steel surface

Different methods and specific processes of rust removal on steel surface;

(1) Manual derusting

Manual derusting tools include hammer, shovel, scraper, wire brush, etc. Generally, the thick rust spots are knocked loose with a hammer, and then removed with a shovel. The labor intensity is high, the derusting efficiency is generally 0.2~0.5m2/h, the environment is harsh, it is difficult to remove scale and other dirt, the derusting effect is not good, and it is difficult to achieve the specified cleanliness and roughness, which has been gradually replaced by mechanical method and chemical method. However, this method is often used to repair ships, especially to repair local defects. For parts that are difficult to reach by mechanical derusting, such as narrow cabins and corners on the opposite side of section steel, manual derusting is also adopted.

(2) Mechanical derusting There are many tools and processes for mechanical derusting, mainly including the following.

1, small pneumatic or electric derusting. It is mainly powered by electricity or compressed air, and is equipped with an appropriate derusting device for reciprocating or rotating motion to meet the derusting requirements of various occasions. Such as angle grinder, wire brush, pneumatic needle beam derusting device, pneumatic rust hammer, tooth-shaped rotary derusting device, etc. , which belongs to semi-mechanized equipment. The tool is light and flexible, which can completely remove rust and old coating and roughen the coating. Compared with manual derusting, the efficiency is greatly improved, reaching 1 ~ 2 m2/h, but the scale cannot be removed and the surface roughness is small. It can be used anywhere, especially in the process of ship repair.

2, shot blasting (sand) derusting. It mainly realizes surface cleaning and proper roughness by particle jet erosion. The equipment includes open shot peening (sand) rust remover, closed shot peening (sand chamber) and vacuum shot peening (sand) machine. The open shot blasting machine is widely used, which can completely remove all impurities such as scale, rust and old paint film on the metal surface, with high derusting efficiency of 4~5m2/h, high mechanization degree and good derusting quality. However, because the abrasive can not be recycled generally, it has an impact on other operations and it is more troublesome to clean up the site. Therefore, the environmental pollution is serious, and its use has been gradually restricted recently.

3, high pressure water abrasive derusting. The impact of high-pressure water jet (plus abrasive grinding) and water pry are used to destroy the corrosion and adhesion of coating to steel plate. It is characterized by no dust pollution and no damage to the steel plate, which greatly improves the derusting efficiency, which can reach more than 15m2/h, and the derusting quality is good. However, after rust removal, the steel plate is easy to rust, so it needs to be coated with special wet rust removal coating, which has a great influence on the coating of general performance coatings.

4, shot blasting derusting. Shot blasting derusting is an advanced mechanical treatment method to remove rust from hull steel by throwing abrasive on the surface of steel with high-speed rotating impeller. It not only has high production efficiency, but also has low cost and high degree of automation. It can realize assembly line operation with little environmental pollution, but it is only operated indoors.

(3) Chemical derusting

The chemical reaction between acid and metal oxide is mainly used to remove the rust products on the metal surface, that is, the so-called pickling rust removal can only be operated in the workshop.