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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. The aforementioned manual, mechanical, sandblasting, and flame rust removal methods 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 paint removers can be used; for example, old oil-based coatings are usually removed using alkaline paint removers, while old coatings made of synthetic resin paints are typically removed with organic solvent-based paint removers. However, due to the corrosive effect of alkaline solutions, and if not controlled properly, they can easily damage the steel surface; therefore, organic solvent strippers are commonly used for removal, with the choice of stripper determined by the type of existing coating. For example, old coatings that were originally oil-based paints, ester resin paints, or phenolic resin paints can be removed using T-1 paint remover ； Old coatings of alkyd resin paint and nitrocellulose paint can be removed using T-2 paint remover ； To achieve a faster paint removal effect, T-3 paint remover should be used, as its effectiveness in removing paint is better than that of T-1 and T-2 paint removers. For old coatings of epoxy resin and polyurethane coatings, although the T-3 stripper can also be used to remove them due to their good adhesion and solvent resistance, the results are poor; therefore, special strippers developed by individual users are usually employed. 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, since the paraffin contained in them often remains on the surface after the old paint has been removed, affecting things such as the adhesion of the new coating, it is necessary to clean the surface with gasoline 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 heat it with an open flame! The entire operation should be carried out in a location free from open flames and with good ventilation, to prevent fires and poisoning.