1. Chemical method (chemical rust removal)
Immerse metal components in acid solution to remove rust, scale and various corrosive substances on the metal surface through chemical reaction.The commonly used acids for pickling are: hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid and hydrofluoric acid, etc.Chemical methods are generally used in factories, and some small components are used more.
2. Physical rust removal
Physical methods can be used: manual derusting, power tool derusting, sandblasting or shot blasting, vacuum sandblasting, flame derusting, high pressure water washing derusting, laser derusting, etc.
3. Manual derusting
Using abrasive cloth, hammer, spatula, scraper, wire brush and other tools to remove rust is simple and convenient for construction, but the labor intensity is high, the quality of rust removal is poor, and the efficiency is low. This method can only be used locally under the conditions that other methods do not have. For example, the trimming of individual components or the local derusting treatment of the installation site.
4. Power tool derusting
Use electric tools or tools driven by compressed air, such as electric grinders, pneumatic grinders, etc. to drive grinding wheels, sandpaper discs, wire discs, etc.Power tools can generally remove all loose scale, rust, old paint and other harmful substances, but cannot remove firmly attached scale, rust and old paint on steel surfaces.
5. Sand blasting and rust removal
A derusting method that uses high-pressure air to bring out abrasives and spray them on the surface of components. The cost of sand is low and the source is wide, such as river sand, sea sand and artificial sand. Now some recyclable sand blasting rooms are gradually using steel sand and steel shot to replace quartz sand and ore sand with low reuse rate. Open type sandblasting has great environmental pollution and has an impact on other operations. It is troublesome to clean up the site and causes serious environmental pollution. It has been gradually restricted in use recently.Vacuum sandblasting is the use of vacuum to immediately recover the sprayed sand particles. This method is used for local rust removal.Sandblasting is divided into dry sandblasting and wet sandblasting
Dry sandblasting: Use 0.5-0.7MPa compressed air to drive sand or steel grit, and spray it onto the steel surface at high speed to remove rust, scale and various corrosive substances on the metal surface. And make the substrate have a certain roughness.Wet sand blasting: use compressed air to bring out the wet abrasives and spray them onto the steel surface at high speed to remove rust, scale and various corrosive substances on the metal surface, which solves the problem of dry sand blasting pollution, but there will be flashes on the surface of the substrate Rust occurs, so corrosion inhibitors should be added. This method has been widely used abroad.Sand blasting is one of the most widely used rust removal methods at present.
6. Shot blasting and derusting
Use the centrifugal force to use the high-speed rotating impeller to throw the abrasive out for surface cleaning, and often use a mixture of steel shot and steel grit as the abrasive for cleaning. This method is generally highly automated and suitable for assembly line production, but not suitable for large and special-shaped workpieces.
7. Rust removal by high-pressure water washing
Using water as the medium, the high pressure is formed by the high pressure generating device, and then it is quickly sprayed out through the nozzle, and the water jet forms a highly concentrated energy, which impacts and grinds the cleaned metal surface like a water arrow. The rust layer and scaling are mostly layered or porous. Once the scale layer is infiltrated, the ultra-high pressure water jet will be inserted between the scale layer and the metal surface in the shape of a wedge, which can remove the scale and old coating on the surface of the workpiece. Also includes very hard corrosion products. The effect is better after adding abrasives to the water.High-pressure water derusting can be divided into two types: high-pressure water plus abrasive sandblasting and pure water sandblasting.High-pressure water plus abrasive blasting: the pressure is generally around 10MPa.High-pressure water pure water sandblasting: water pressure generally reaches 150-200MPa, or even higher.
8. Flame derusting
Flame derusting is one of the derusting processes. The code name of flame derusting is Ft. The main process is to shovel off the rust layer on the surface of the substrate, then bake or heat it with flame, and use a power wire brush to clean the heated surface.