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The removal of the old coating depends on the degree of damage to the coating film and the specific requirements for it; it can be removed entirely or partially. Physical methods such as manual labor, machinery, sandblasting, and flame rust removal can all be used to remove old coatings. In addition, strippers are widely used to remove old coatings. For coatings with different film-forming substances, different stripping agents can be used; for example, old oil-based coatings are usually removed using alkaline stripping agents, while old coatings made of synthetic resin paints are typically removed with organic solvent-based stripping agents. However, due to the corrosive effect of alkaline solutions, and if not controlled properly, they can easily damage the steel surface; therefore, organic solvent degreasers are commonly used for removal, with the choice of degreaser determined by the type of existing coating. When using a paint remover to remove the old coating, first remove dust, moisture, and oil from the surface of the part to be treated. Then apply the paint remover to the old coating using a bristled brush, applying a thick layer of it. Wait for about ten minutes (this time should be extended in winter); once the old coating swells or softens, it can be gently removed with a spade. If the old coating is thick, it can be applied several times to remove it. When using organic solvents to remove paint, the paraffin contained in them often remains on the surface after the old paint has been removed, which can affect the adhesion of the new coating; therefore, it is necessary to clean the surface thoroughly with solvents or similar substances. The role of paraffin in the paint remover is to slow down the evaporation of organic solvents, allowing it to act on the old coating for a longer period of time. When the temperature is too low, paraffin will precipitate, affecting the paint removal effect. Therefore, the paint remover should be placed in a place with a higher temperature, and used after it has melted evenly. Be sure not to use an open flame for heating! The entire operation should be carried out in a location free from open flames and with good ventilation, to prevent fires and poisoning.