CN-121992387-A - Environment-friendly chemical passivating agent for aluminum alloy surface as well as preparation method and application thereof

Abstract

The invention relates to an aluminum alloy surface environment-friendly chemical passivating agent, and a preparation method and application thereof, and belongs to the technical field of metal surface treatment. The passivating agent is in a liquid state, and is prepared from the following raw materials of 60-80 g/L potassium permanganate, 36-g/L aluminum sulfate, 0-54 g/L stabilizer, 0.9-1.2 g/L concentrated sulfuric acid 100-ml/L-200 ml/L and the balance of water in each liter of solution, wherein the stabilizer consists of sodium stannate, sodium pyrosulfate and 8-hydroxyquinoline, and the passivating agent is prepared by fully mixing the raw materials. The application method comprises the steps of immersing the aluminum alloy with the clean and dry surface in an implementation passivating agent, so that a passivation layer can be formed on the surface of the aluminum alloy, the application treatment time is shortened to 0.5-2 min, and meanwhile, the applicable temperature range is expanded to 35-50 ℃, so that the feasibility of industrial production is greatly improved.

Inventors

• LIU BIN
• JIANG WENBO
• NING YUJIE

Assignees

• 北京化工大学

Dates

Publication Date

20260508

Application Date

20251231

Claims (5)

1. 1. The environment-friendly chemical passivating agent for the aluminum alloy surface is characterized by being in a liquid state, wherein the raw material formula comprises 60 g/L-80 g/L potassium permanganate, 36 g/L-54 g/L aluminum sulfate, 0.9 g/L-1.2 g/L stabilizer, 100 ml/L-200 ml/L concentrated sulfuric acid and the balance of water in each liter of solution; the stabilizer consists of sodium stannate, sodium pyrosulfate and 8-hydroxyquinoline; the concentrated sulfuric acid is sulfuric acid solution with the mass fraction of 98%.
2. 2. A method for preparing the environment-friendly chemical passivating agent for aluminum alloy surfaces, which is characterized by comprising the following steps of: (1) Adding concentrated sulfuric acid into water, stirring, and fully mixing to form a solution A; (2) Adding potassium permanganate into the solution A, stirring, and fully mixing to form a solution B; (3) Adding a stabilizer into the solution B, and fully mixing to form a solution C; (4) Adding aluminum sulfate into the solution C, stirring, and fully mixing to prepare the aluminum alloy surface environment-friendly chemical passivating agent.
3. 3. The method for preparing the environment-friendly chemical passivating agent for the aluminum alloy surface, which is disclosed in claim 2, is characterized in that in the step (1), the mixing time is 20 min-30 min, and the rotating speed is 400 r/min-500 r/min; In the step (2), the mixing time is 50 min-60 min, and the rotating speed is 400 r-500 r/min; in the step (3), the mixing time is 5 min-10 min, and the rotating speed is 400 r-500 r/min; In the step (4), the mixing time is 20 min-30 min, and the rotating speed is 400 r-500 r/min.
4. 4. The application of the environment-friendly chemical passivating agent for the aluminum alloy surface, which is characterized in that the aluminum alloy with clean and dry surface is soaked in the environment-friendly chemical passivating agent for the aluminum alloy surface, which is described in claim 1, and a passivation layer is formed on the aluminum alloy surface.
5. 5. The application of the environment-friendly chemical passivating agent for aluminum alloy surfaces, as claimed in claim 4, wherein the soaking temperature is 35-50 ℃ and the soaking time is 30 s-120 s.

Description

Environment-friendly chemical passivating agent for aluminum alloy surface as well as preparation method and application thereof Technical Field The invention relates to an aluminum alloy surface environment-friendly chemical passivating agent, and a preparation method and application thereof, and belongs to the technical field of metal surface treatment. Background Aluminum alloys have found very wide application in terms of their light weight, high strength, good thermal and electrical conductivity, excellent corrosion resistance and good processability. The aluminum alloy has relatively low density and high strength, which makes the aluminum alloy have outstanding technical advantages and development potential in the fields of aerospace, high-speed ship, automobile manufacturing and the like, which need to reduce weight while maintaining structural strength. In the aspect of corrosion resistance, a layer of relatively dense oxide film can be spontaneously formed on the surface of the aluminum alloy, so that the corrosion of various chemical substances can be effectively resisted, and the corrosion resistance of the material is improved. The aluminum alloy is also easy to process into various shapes and sizes, has good plasticity and ductility, and is suitable for manufacturing complex structures. However, in the service environment containing chloride ions, sulfate ions, heavy metal ions or extreme pH values (acidic/alkaline), the natural oxide film spontaneously formed on the surface of the aluminum alloy has limited protective capability, so that the problems of pitting corrosion, intergranular corrosion, stress corrosion cracking and the like easily occur, and the reliability and service life of the component are seriously threatened. To overcome this weakness, passivation has become a critical surface protection technique for improving the corrosion resistance of aluminum alloys. The technology forms a passivation layer thicker, denser and higher in chemical stability than a natural oxide film through the reaction of a chemical agent and the metal surface, and effectively blocks corrosive medium. Among the passivation technologies, the passivation of chromates (particularly hexavalent chromium) has been dominant in high-end industrial fields such as aerospace, military industry and the like for a long time due to its mature process, relatively low cost, extremely excellent corrosion resistance of the formed passivation film, unique self-repairing capability, and excellent adhesion with subsequent coatings. However, chromate passivation techniques have serious drawbacks that are difficult to overcome. Hexavalent chromium is internationally recognized strong carcinogen and allergen, and constitutes a great threat to the health of operators, and chromium-containing wastewater and waste residues generated in the production and use processes are difficult to treat, high in cost and improper in treatment easily causes serious soil and water pollution. In addition, increasingly stringent environmental regulations worldwide impose severe restrictions or even prohibitions on the use and emissions of hexavalent chromium, so that the application space of hexavalent chromium under the concept of sustainable development is greatly compressed. In view of environmental and health risks associated with chromate passivation, developing efficient and environmentally friendly alternative aluminum alloy chemical passivation techniques has become an urgent industry requirement. Many non-chrome substitution techniques currently under investigation include molybdate passivation, rare earth salt (e.g., cerium salt) passivation, silane/zirconium titanium based passivation, organic acid/phytic acid passivation, and the like. The molybdate passivation principle is similar to that of chromate, toxicity is reduced, corrosion resistance is relatively better, and the process is mature, but the main defects are that cost is high, self-repairing capability of a passivation film is generally lower than that of the chromate film, and a certain environmental concern exists in high-concentration molybdate. The rare earth salt passivation provides barrier protection by depositing a rare earth oxide/hydroxide film, has outstanding environmental protection performance, but has slower film forming speed, strict process control (such as pH value and temperature) requirements, and the uniformity and adhesive force of a film layer cannot meet the requirements, so that the cost benefit of large-scale application still needs to be optimized. The silane/zirconium titanium passivation is based on organic and inorganic hybridization reaction to form a nano protection layer, is environment-friendly and nontoxic, has excellent binding force with an organic coating, however, the corrosion resistance, particularly the long-term corrosion resistance and scratch resistance, of a pure silane film are very lower than those of a chromate film, the requireme