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Aluminum profile was electropolished with no chromic acid electrolyte
Content source: http://huichenglawyer-sy.com Author: military general release date: June 2, 2020 08:30 reading times: 1037 times Click collection

For the phosphoric acid based electrolytic polishing process without hexavalent chromium, the additives to make the electrolyte have high viscosity and prevent the surface corrosion of aluminum profiles are the same as those of the hexavalent chromium electrolytic polishing process; the increase of viscosity is also realized by aging the electrolytic polishing solution; the additives to prevent the surface corrosion of aluminum profiles are mostly some polyorganic acids containing alcohol hydroxyl groups, low-grade monohydric alcohols and polyhydric acids And polyol polymer PEG In the electrolyte, a network adhesive layer will be formed on the surface of aluminum profile, which can play the role of thickening and preventing corrosion Aluminum profile Surface corrosion can also be added nitric acid in the electrolyte, such as in the United States patent USP 3.530.048 This kind of electrolyte is composed of phosphoric acid, sulfuric acid, aluminum phosphate, nitric acid and copper sulfate and can obtain high brightness;

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  The principle of electropolishing without chromic acid electrolyte based on phosphoric acid is basically the same as that containing chromic acid, so it will not be discussed any more. At present, there are many formulas of electrolytic polishing without chromic acid introduced in domestic materials, but they are basically the same. The electrolyte added with multiple organic acids or alcohols is easy to change color in the case of high concentration sulfuric acid and heating, and the addition of low-grade alcohol is easy to ignite It is reported that among these additives, alcohols have the best corrosion inhibition effect on electropolishing, which may be due to the fact that alcohols contain bases (1 OH The high acidic hydrogen ions acting on the anode surface are beneficial to the interface pH Among these alcohols, ethanol, glycerol and n-butanol are the best, and n-butanol is the best, but n-butanol is more toxic, easy to volatilize and burn, and the cost is also high; the cost of ethanol is the lowest, but the disadvantage is easy to ignite; glycerol has high flash point, is not easy to burn, but the viscosity is too high, the cost is high, and the capacity is high It is easy to produce a large amount of foam; low-grade alcohol has low boiling point and flash point, so it is too dangerous to add directly in production, so it can only be added after mixing with phosphoric acid; polyols or alcohol ethers, with high boiling point and high flash point, bring convenience for direct addition in production, but it is easy to produce large amount of foam, which is also easy to ignite (not burn) and produce burst sound in production;



Small alcohols can be associated by hydrogen bond, and the associated alcohol molecules can be polished in the Aluminum profile The viscous film formed on the surface of aluminum profile makes the surface of aluminum profile have stable passivation state, which is also an important reason that small molecule alcohols can be used as good additives in electropolishing;


For polyols, their molecular chain length can form irregular coil flow in the solution, and there are also different degrees of association between macromolecules. These factors make the viscosity of macromolecular alcohols greater than that of small molecular alcohols. From the perspective of the mucosal theory of electropolishing, it is undoubtedly correct to use polyols as additives in electropolishing, but what is the molecular weight of polyols Polymer alcohol and its addition amount are important for electropolishing; if the molecular weight is small, the effect is not obvious; if the molecular weight is large and the addition amount is small, the viscosity of the solution will be too high, and the excessive viscosity will not be conducive to the activation of micro convex part of aluminum profile, and hinder the renewal of acid solution at this place, so that the anodic dissolution products can not smoothly go deep into the electrolyte Diffusion is not conducive to the leveling effect; meanwhile, the anodic dissolution products on the surface of aluminum profiles are not easy to diffuse, which makes the electrolyte viscosity further increase. Finally, due to the destruction of the balance between the formation rate and dissolution rate of the oxide film, the defects such as frosting will occur, which will lead to the failure of leveling and polishing process. The molecular weight and addition amount of polyol should be determined according to the type of aluminum profile The class and surface requirements are determined by experiments with reference to the introduction of relevant materials;


The adhesive film formed by the association of small molecular alcohols through hydrogen bonding is mainly formed on the surface of aluminum profiles. This layer of surface viscous film is very thin, which will not hinder the diffusion of anodic dissolution products to the depth of electrolyte in the process of electrolytic polishing, so that the leveling effect of the whole polishing process is relatively constant; macromolecular multi polymer alcohols will increase the viscosity of the whole electrolyte, which is easy to hinder the anode If the dissolution product diffuses to the depth of the electrolyte, improper control will affect the constant leveling action in the electrolysis process; this is also the reason why small molecular weight alcohols are used more in electrolytic polishing; however, it is undeniable that the appropriate molecular weight of alcohol is suitable PGE It is superior to small molecular alcohols in leveling and corrosion inhibition PEG It is also a research direction;


Polymer alcohols are often used in electropolishing PEG Low molecular weight polyethylene glycol (lmw-peg) is a colorless and transparent liquid, which becomes white paste, white wax or white solid with the increase of molecular weight. According to the mucosal theory of electropolishing, the author thinks that it is better to use liquid low molecular weight polyethylene glycol; in order to prevent the electrolyte from discoloration in the production process, phosphoric acid can also be used - Sulfuric acid is mixed with acid and phosphoric acid is used - Other organic or inorganic acids, and then add alcohols as corrosion inhibitors, so as to prevent the discoloration of the electrolyte in the production process; tartaric acid and oxalic acid are feasible choices, boric acid is a weak acid, and it has three hydroxyl groups. In strong acid electrolyte, it is a kind of "alkali", which can neutralize hydrogen ions on the anode surface to reduce its acidity, which is beneficial to prevent the electrolyte from discoloration Aluminum profile Corrosion of the anode surface; therefore boric acid is used - Phosphoric acid or adding other organic acids to form a mixed acid electrolyte is also a development direction;


In general, the electrolytic polishing process of aluminum profile is not better than that of electrolytic polishing in some special occasions. However, there is no need for electrolytic polishing process in domestic It is mature, which brings many difficulties to the simple field control required by mass production; the second is the life of electrolysis, which directly affects the comprehensive cost of electrolytic polishing of aluminum profiles; the third is that although high reflectivity can be obtained, some fine stripes are easy to appear on the surface. Some foreign patents introduce adding neutral suspended particles, such as silica and pumice, into this electrolyte However, a lot of experimental work is needed;


In the future, the key problem in the development of electrolytic polishing without chromic acid based on phosphoric acid is how to find the most suitable one or several kinds of organic substances that can be used in the electrolytic polishing of aluminum profiles: the process is stable and easy to control; the electrolyte life is not lower than that of chromic acid process; the brightness and smoothness of electropolishing is better than that of chromic acid process; the comprehensive cost of electropolishing is not higher than that of electropolishing The requirements of chromic acid containing process, only when these points are achieved, can electrolytic polishing without chromic acid have wide application value;


The two-step process can be used to improve the electropolishing process with or without chromic acid Aluminum profile In the first polishing, high sulfuric acid and low phosphoric acid were used to eliminate the polishing line and improve the brightness. In the second polishing, high phosphoric acid and sulfuric acid were used to quickly polish;

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Contact APAs / contact us
Tianjin Aipu industrial aluminum profile Co., Ltd
Tel: 022-87920088
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Service hotline: 137021119190 (24-hour service hotline)
Q        Q: five hundred and thirty-four million nine hundred and seventy-three thousand nine hundred and six
Email address: lxc@apas.com.cn
Address: a3-2 Saida international industrial city, Xiqing Economic and Technological Development Zone, Tianjin
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