The key to improving the corrosion resistance of aluminum foil tissue paper lies in optimizing the surface treatment process. Traditional aluminum foil tissue paper, due to its uneven surface oxide layer or microscopic defects, is susceptible to pitting and crevice corrosion in humid, salt spray, or chemical environments, leading to packaging failure or product deterioration. Targeted surface treatment can significantly enhance its corrosion resistance and extend its service life.
Anodizing is a classic method for improving the corrosion resistance of aluminum foil tissue paper. This process uses an electrochemical reaction to form a dense aluminum oxide film on the surface of the aluminum foil. The film can be several microns to tens of microns thick, with low porosity and high hardness. The oxide film formation process occurs in three stages: First, the aluminum foil surface dissolves in an acidic electrolyte, generating aluminum ions. Next, the aluminum ions combine with oxygen in the electrolyte to form aluminum oxide. Finally, the aluminum oxide film densifies under the action of an electric field, sealing the surface pores. Aluminum foil tissue paper that has undergone anodizing can withstand salt spray tests for hundreds of hours, far exceeding untreated samples. This makes it particularly suitable for applications such as food and pharmaceuticals, where tight sealing is crucial.
Chemical conversion coating technology involves reacting aluminum foil tissue paper with a specific chemical solution to create a conversion coating with strong adhesion and excellent corrosion resistance. Common conversion coating types include chromate, phosphate, and silane. Chromate coatings, due to their hexavalent chromium content, are environmentally limited; phosphate coatings are low-cost but offer limited corrosion resistance; and silane coatings are the mainstream due to their chromium-free and excellent corrosion resistance. The formation of silane conversion coatings relies on the hydrolysis and condensation reaction of silane coupling agents. The silanol groups in the silane coupling agents combine with the hydroxyl groups on the aluminum foil surface to form chemical bonds, enhancing the film's adhesion. This process reduces the corrosion current density of aluminum foil tissue paper in a 3.5% sodium chloride solution by an order of magnitude, significantly improving its pitting resistance.
The coating composite process applies an organic or inorganic coating to the surface of aluminum foil tissue paper, creating a physical barrier that prevents corrosive media from contacting the substrate. Common coating materials include organic coatings such as epoxy resins, polyurethanes, and acrylates, as well as inorganic coatings such as alumina and silica. Among these, the micro-dimpled coating process has attracted considerable attention for its ability to achieve uniform double-sided coating. This process transfers the coating to the aluminum foil surface using a micro-dimpled roller, which then forms a smooth, dense coating after oven drying. The aluminum foil tissue paper treated in this way exhibits strong adhesion to the substrate and excellent solvent and abrasion resistance, making it particularly suitable for applications requiring extremely high corrosion resistance, such as lithium battery packaging film.
Pretreatment is also crucial for enhancing the corrosion resistance of aluminum foil tissue paper. Pretreatment, including degreasing, degreasing, and alkaline cleaning, aims to remove oil stains, oxide layers, and impurities from the aluminum foil surface, providing a clean, activated surface for subsequent processing. For example, alkaline cleaning solutions effectively remove the natural aluminum oxide layer on the surface of aluminum foil while increasing the wettability of the corrosive solution on the foil, facilitating the uniform formation of subsequent conversion films or coatings. Pretreated aluminum foil tissue paper reduces surface roughness and improves film adhesion, thereby enhancing overall corrosion resistance.
Multi-layer lamination processes combine aluminum foil tissue paper with other materials (such as paper and plastic film) to form a synergistic protection system, further enhancing corrosion resistance. For example, in the production of corrosion-resistant aluminum foil, the base paper layer, aluminum foil layer, and corrosion-resistant layer are thermally bonded together, creating a secure bond between the layers. The corrosion-resistant layer effectively blocks the penetration of corrosive media such as moisture and oxygen. This process not only improves the corrosion resistance of aluminum foil tissue paper, but also enhances its mechanical strength and processing adaptability, making it suitable for complex packaging scenarios.
