What are the methods of steel derusting?

After the steel is rusted, the rust is loose, and the adhesion with the metal surface is not firm. The paint coated on the rust will inevitably cause the coating to fall off, resulting in the failure of the anti-corrosion coating. Derusting can be said to be a process that cannot be bypassed by any coating process. Derusting methods can be divided into chemical and physical methods.

1. Chemical derusting: immerse metal components in acid solution, and remove rust, oxide skin and various corrosive substances on the metal surface through chemical reaction. Common acids for pickling include hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid and hydrofluoric acid.Chemical derusting is generally used in factories, and some small parts are used more.

2. Physical derusting: physical derusting can adopt manual derusting, power tool derusting, sand blasting derusting, flame derusting, high-pressure water flushing derusting, etc.

manual rust removal: use abrasive cloth, hammer, shovel, scraper, Wire Brush and other tools to remove rust, which is simple and convenient for construction, but it has high labor intensity, poor rust removal quality and low efficiency. This method is applicable to the trimming of individual parts or other local derusting treatment.

power tool derusting: use electric grinder, pneumatic grinder and other tools to drive the grinding wheel, sandpaper tray, steel wire tray, etc. for derusting. Generally, power tools can remove all loose oxide skin, rust, old paint film and other harmful substances, but they cannot remove the oxide skin, rust and old paint film firmly attached to the steel surface.

Sand blasting and derusting: a rust removal method that uses high-pressure air to bring out abrasive and spray it onto the surface of components. Open sandblasting has great environmental pollution and impact on other operations. It is troublesome to clean the site and has serious environmental pollution. Recently, its use has been gradually restricted. Vacuum sand blasting is to use vacuum to immediately recover the sprayed sand. This method is used for local rust removal. Sand blasting is divided into dry sand blasting and wet sand blasting. Dry sand blasting: use 0.5-0.7mpa compressed air to drive sand or steel sand, and spray it to the steel surface at high speed to remove rust, oxide skin and various corrosive substances on the metal surface. And make the substrate have a certain roughness. Wet sand blasting: use compressed air to take out the wet abrasive and spray it on the steel surface at high speed to remove rust, oxide skin and various corrosive substances on the metal surface, which solves the problem of dry sand blasting pollution, but there will be flash rust on the surface of the substrate, so corrosion inhibitor should be added.

high pressure water flushing and derusting: take water as the medium, form high pressure through the high pressure generator, and then spray it quickly. 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 distributed in layers or multi pores. Once the scale layer is penetrated, the ultra-high pressure water jet is wedged between the scale layer and the metal surface, which can remove the oxide skin, old coating, etc. on the workpiece surface, including very hard corrosion products. The effect is better after adding abrasive in water.

flame derusting: flame derusting is one of the derusting processes. The code 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 clean the heated surface with a power wire brush. This method is applicable to the removal of old anti-corrosion coating (paint film) or metal surface engineering with oil immersion. It is not applicable to thin-walled metal equipment and pipelines, nor can it be used in the rust removal engineering of annealed steel and hardenable steel.