Thread Content
What are the methods for removing rust from steel surfaces? What are its characteristics and applications? There are many methods for removing rust from steel surfaces, and the commonly used ones include the following: 1. Manual rust removal: Using manual tools such as iron sandpaper, scrapers, shovels, and wire brushes to remove rust. This method requires high labor intensity and has low production efficiency, but it is simple and flexible to operate, and is still in use to this day. 2. Mechanical rust removal: Rust is removed through the impact and friction generated by mechanical power; the most commonly used tools for this purpose include air brushes, rust removal guns, electric brushes, and electric grinding wheels. 3. Jet rust removal: Using mechanical centrifugal force or compressed air, high-pressure water, etc. as power, abrasives (sand, gravel, or iron pellets) are sprayed at high speeds onto the surface of the workpiece through specialized nozzles. The impact and friction forces generated thereby remove contaminants (including damaged old paint) and rust, resulting in high production efficiency and good treatment quality. The sandblasted steel surface has a slightly serrated texture, which enhances the adhesion between the coating and the steel surface. However, its roughness must absolutely not exceed 1/3 of the coating thickness. Common methods for rust removal by sandblasting include dry sandblasting, wet sandblasting, dust-free sandblasting, and high-pressure water sandblasting. Dry sandblasting generates a lot of dust, which is harmful to the environment and poses health risks ； Although the wet method produces no dust, moisture causes the surface to rust again. To prevent this, 1% to 1.5% of an anti-rust agent (such as trisodium phosphate, sodium carbonate, sodium nitrite, etc.) along with an emulsifier or soapy water is added to the water, so that the surface does not rust again in the short term; after that, a maintenance primer is applied. Dust-free sandblasting involves continuously cycling processes such as sand addition, sandblasting, and sand collection within a closed system to prevent dust from flying around. High-pressure water jetting is mainly used for large-scale rust removal, such as on ship hulls, oil tanks, storage tanks, boilers, etc.; passivators and soapy water are often added to the water as well. 4. Flame rust removal: Utilizing the difference in thermal expansion coefficients between steel and scale, an oxygen-acetylene burner is commonly used to heat the steel, causing the scale to flake off. It is mainly used for thick steel components and large castings, etc., and cannot be used for thin steel materials or small castings, as otherwise the workpiece will deform due to heat, affecting its quality. 5. Chemical rust removal: This method involves using acid solutions to undergo a chemical reaction with iron oxides, thereby dissolving and removing the surface rust layer to achieve rust removal. Therefore, it is also known as \"pickling\" for rust prevention. It is commonly used for rust removal on small workpieces and those with complex shapes. It’s very efficient. However, there is slight dissolution loss of steel and hydrogen embrittlement occurs. There are many formulas for chemical rust removal; typically, an aqueous sulfuric acid solution at 7% to 15% concentration (or with 5% table salt added) is used as the acid cleaning solution for rust removal. To prevent sulfuric acid from corroding steel, small amounts of corrosion inhibitors such as robutin and thiourea can be added. In addition, different acid cleaning and rust-removing solutions can also be prepared using phosphoric acid, nitric acid, hydrochloric acid, etc. There are many methods of pickling, with immersion pickling and spray pickling being commonly used. In addition, pickling paste treatment is also used, depending on the specific conditions.