During the degreasing, polishing, alkaline etching, and texture etching of the profile radiator, an insoluble oxide layer will form on the surface of the workpiece. This oxide layer is just a loose structure attached to the surface of the workpiece and must be removed by acid etching. The acid etching mentioned here does not need to corrode the aluminum profile matrix, but only needs to dissolve the insoluble oxide on the surface of the workpiece. Acid etching, also known as acid light, is a method used in many industry standards. Nitric acid is used to remove corrosion residues on the surface of aluminum alloy workpieces to expose the bright base metal surface.
Acid etching is usually carried out in a nitric acid solution of a certain concentration. An appropriate amount of chromic anhydride can also be added as needed. If it is a cast aluminum alloy with a high silicon content, an appropriate amount of hydrofluoric acid or ammonium bifluoride should be added to the nitric acid solution. In addition to nitric acid, sulfuric acid and phosphoric acid can also be used for aluminum alloy pickling, but strong oxidants are required. Organic acids are of little practical significance in aluminum alloy pickling.
Sulfamic acid has a good pickling effect on many aluminum alloys, but when pickling with sulfamic acid, oxidizing substances cannot be added to the sulfamic acid solution; sulfamic acid can be used to treat some insoluble metal oxides by complexation; in nitric acid and sulfuric acid solutions with oxidants, some insoluble metal oxides can be oxidized from insoluble low-valent states to soluble high-valent states.
Aluminum alloy pickling can be divided into ordinary pickling and bright pickling according to the concentration of acid solution. Bright pickling here does not refer to chemical polishing, but a pickling method that can keep the back of the aluminum alloy surface bright. It is mostly used for surface pickling after chemical polishing, electrolytic polishing, alkaline etching, texture etching and other treatments. Bright pickling is generally used for aluminum alloy surface treatment.
Profile radiator pickling is also one of the most widely used processes in aluminum alloy surface treatment. Almost every process in the entire pre-treatment process will undergo pickling, and its application frequency is second only to water washing.
