Discuss several methods for rust removal from steel surfaces, along with their characteristics and applications

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This post was last edited by Wang Wei2 on 2024-2-11 at 10:35. Let’s discuss several methods for rust removal from steel surfaces, along with their characteristics and applications. There are many ways to remove rust from steel surfaces, and the following are some of the commonly used methods: 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. Small steel parts can be placed in wooden barrels filled with yellow sand or wood chips, and rotated at a speed of 40 to 60 revolutions per minute; rust is removed through collision and friction, resulting in high production efficiency and good rust-removal quality, which has led to its widespread use. 3. Jet rust removal: Using mechanical centrifugal force or compressed air, high-pressure water, etc. as power, abrasives (sand, gravel, or iron pellets) are ejected 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; this method offers high production efficiency and good treatment quality. The surface of steel after sandblasting is slightly serrated, 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 15% of rust inhibitors (such as trisodium phosphate, sodium carbonate, sodium nitrite, etc.) along with emulsifiers or soapy water are added to the water, so that the surface does not rust again for a short period of time; 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: Taking advantage of the different thermal expansion coefficients of steel and scale, an oxyacetylene 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 makes use of chemical reactions between acid solutions and iron oxides to dissolve and remove the rust layer on the surface, thereby achieving 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%–15% concentration (or with 5% salt added) is used as the acid cleaning solution for rust removal. To prevent sulfuric acid from corroding steel, a small amount of corrosion inhibitors such as ribodine and thiourea can be added. In addition, different acid pickling 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.