Rust is an oxide formed by the contact of metal surface with oxygen, water and acids in the air, such as Fe0, Fe3O4, FeO3, etc. It is usually called rust. The main methods of rust removal for diesel generating units are mechanical method, chemical pickling method and electrochemical etching method. Below by Kang Bang Xiaobian for your detailed introduction below.
(1) Mechanical method
Apply friction and cutting between mechanical parts to remove rust layer on the surface of parts. Common methods include brushing, grinding, polishing and sandblasting. Small batch repairs depend on manual brushing, scraper, sand cloth and other brushing, scraping or polishing rust layer. Batch parts or conditional units can be driven by motors or wind turbines to stop rust removal by various rust removal tools, such as electric polishing, polishing, rolling, etc. Sandblasting rust removal is the application of compressed air, a certain size of sand through the gun sprayed on the rust surface of parts. It not only removes rust quickly, but also prepares for painting, spraying, electroplating and other processes. After sandblasting, the surface is clean and has a certain roughness, which can improve the separation force between the cover layer and the parts. Mechanical rust removal can only be used in the appearance of unimportant mechanical parts.
(2) Chemical method
This is an acid pickling process that uses chemical reactions to dissolve rust products on the surface of metals. The principle is that the dissolution of metal by acid and the mechanical action of hydrogen produced in chemical reaction on rust layer make rust layer scattered. Commonly used acids include hydrochloric acid, sulfuric acid, phosphoric acid, etc. Because of the different materials of metals, the chemicals used to dissolve rust products are also different. The selection of rust-removing chemicals and their operating conditions are mainly determined by the variety of metals, chemical composition, external expression, dimensional accuracy and external quality of parts.
(3) electrochemical etching
It is to place the parts in the electrolyte through direct current, through chemical reaction to achieve the purpose of rust removal. This method is faster than chemical method, can better preserve the matrix metal, acid consumption is less. Generally, there are two kinds: one is to use the rusted parts as the anode; the other is to use the rusted parts as the cathode. Anodic rust removal is due to the dissolution of metal after electrification and the tearing of rust layer by oxygen in the anode. The cathode rust removal is due to the hydrogen generated on the cathode after electrification, which restores iron oxide and tears the rust layer by hydrogen, so that the rust is scattered from the surface of the parts. The main defect of the former is that when the current density is too high, it is easy to corrode excessively and destroy the appearance of parts, so it is suitable for parts with simple shape. Then, although there is no corrosion problem, hydrogen easily enters the metal, resulting in hydrogen embrittlement and reducing the plasticity of the parts. Therefore, it is necessary to confirm the appropriate rust removal method according to the detailed condition of the rusted parts.