ã€China Aluminum Network】 The quality of aluminum sulfate anodized oxide film is good or bad, and the reliability of the anti-corrosion protection depends on the composition of the aluminum alloy, film thickness and anodizing process conditions such as temperature, current density, and water quality. And anodized after the filling and sealing process. To reduce or avoid the anodization failure to improve the quality of products to start from the fine point, take effective measures.
(1) For different aluminum alloys, such as casting molding, calendering, or machining or heat treatment welding, select the appropriate pretreatment method according to the actual situation. For example, the non-machined surface of the cast aluminum alloy should generally be sandblasted or shot blasted to remove its original oxide film, sticky sand, etc. For aluminum alloys with high silicon content (especially cast aluminum), it should be etched and activated by nitric acid mixed acid solution containing about 5% hydrofluoric acid to effectively maintain a good activated surface and ensure the quality of the oxide film. Aluminum alloys of different materials, bare aluminum and pure parts, or aluminum and aluminum alloy parts of different sizes and sizes are generally not suitable for oxidation treatment in the same tank.
For lapped, spot welded or riveted aluminum alloy assemblies, for the aluminum alloy parts that are easily formed in the anodizing process and are not easy to exclude from the airbag, the sulfuric acid anodizing process is generally not allowed from the viewpoint of quality.
(2) The mounting fixture material must ensure good electrical conductivity. Generally, hard alloy rods are used. The panel must ensure certain elasticity and strength. The hook should use copper or copper alloy material. Used special or general-purpose fixtures, such as those re-used during anodization, must be completely removed from their surface oxide film to ensure good contact. Fixtures must not only ensure sufficient conductive contact area, but also minimize fixture impressions. If the contact surface is too small, it can lead to erosion of the anodized parts.
(3) The temperature of the sulfuric acid anodizing solution must be strictly controlled, and the preferred temperature range is 15 to 25°C. Sulfuric acid anodizing process requires the use of compressed air mixing, and should be equipped with refrigeration equipment. In the case of no refrigeration device, the addition of 1.5% to 2.0% of tricarboxylic acid or carboxylic acid such as oxalic acid, lactic acid, etc. to the sulfuric acid electrolyte can make the anodizing solution temperature range exceed 35°C to avoid or reduce the loosening of the oxide film. Powdering. Some process tests and production practices have confirmed that the addition of an appropriate amount of carboxylic acid or glycerin to the anodizing electrolyte of sulfuric acid can effectively reduce the adverse effects of the reaction heat effect, and can improve the anodized electrolysis without reducing the thickness and hardness of the oxide film. The temperature of the liquid is allowed to an upper limit, and the production efficiency is improved on the premise of ensuring the quality. In addition, under the condition of constant temperature control, it is necessary to pay attention to the effective control of the anode current density in order to better ensure the quality of the oxide film.
(4) Sulfuric acid anodic oxidation The water used in the electrolyte and the harmful impurities in the electrolyte must be strictly controlled. Preparation of sulfuric acid anodizing solution should not use tap water, especially can not use turbid water containing Ca2+, Mg2+, SiO32- and Cl- high content of tap water. Under normal circumstances, Cl- concentration of 25mg/L in water will have a detrimental effect on the anodizing treatment of aluminum alloys. Cl- (including other halogen elements) can damage the oxide film and even form oxide films. Sulfuric acid anodization should use softened water, deionized water or distilled water, Ccl-≤15mg/L in the electrolyte, and total minerals ≤50mg/L.
Sulfuric acid solution will produce oily foam and suspended impurities during the anodizing process and should be periodically removed. Other harmful impurities commonly found in sulfuric acid plate oxidation solutions include Cu2+, Fe3+, and Al3+. If the impurity content exceeds the allowable content, harmful effects may occur, and the sulfuric acid solution may be partially or completely replaced in order to effectively ensure the quality of anodized aluminum alloy sulfate.
Aluminum sulfate anodizing treatment is a widely used and mature anti-corrosion protection decoration treatment process. As long as the strict implementation of process conditions and careful operation, the quality of sulfuric acid anodic oxide film is completely guaranteed.
Effective Butachlor,Neonicotinoid Dinotefuran,Effective Glufosinate-ammonium
Shandong Qiaochang Chemical Co., Ltd. , http://www.hzchemicals.com