1, process introduction
In recent years, the production and sales volume of aluminum alloy matt profiles has been increasing, with a market share of over 80%. At present, the production of matt profiles generally uses alkaline etching methods, and the aluminum dissolved losses range from 3% to 5%, which results in huge waste of resources, greatly increases the difficulty of environmental protection management, and aggravates the “three wastes†processing burden of the company. Acid etching technology is developed for the lack of alkali etching methods, in principle, completely different from the alkaline pitting matt surface treatment. The process mainly adopts a unique method to generate a highly uniform and high-density molecular point corrosion on the surface of the aluminum profile, and by improving the material structure of the profile at the surface of the profile, thereby achieving the effect of smoothing the surface and eliminating the surface defects caused by the metallurgical process (for example, eliminating the extrusion Indentation, masking of the weld line, and mitigation of defects such as coarse grains, make the aluminum surface smooth and delicate, soft metallic luster, greatly improving the surface quality of aluminum profiles. With the acid-etched matt process, the aluminum melt loss is between 0.5% and 0.8%, which reduces the production cost to less than half of the traditional matt process, and the production efficiency has a substantial increase, which is of great practicality. Economic Value.
2, etching mechanism
Etching is chemical etching under certain conditions. The aluminum profile contacts the etching solution and reacts rapidly to form the complex in a very short time. The reaction equation is as follows:
3F-+A1-A1F3
6F-+A13+-A1.F63-
A1F63-+A12O3.3H2O-A13(OH)3F6+30H-
The resulting complex has a certain viscosity and easily adheres to the surface of the aluminum substrate to form a protective film. Extruded profiles generally have many slight marks. They are peaks observed under high power microscope. The protective film adhering to the aluminum matrix is ​​thicker in the recesses, thinner at the bulge, and has a greater chance of contact with the etching solution at the thin parts. , can continue to dissolve faster; thick areas are shielded by adherents to slow down the dope reaction rate, due to the difference in the rate of dissolution of the concave and convex parts, so as to achieve a smooth surface, eliminate extrusion marks (sand surface) Asia Light effect. Relieving coarse grain and weld line is directly related to the specific properties of acid etching. In the production of aluminum profiles, coarse grain and weld line are closely related to the die, extrusion process and the homogenization of the cast rod. The deeper the alkali etching, the more severe the coarse crystal and the weld line. Due to the fast acid etching time and short time, the reaction has ended without the occurrence of severe coarse grains and weld lines. Therefore, the acid etching process can effectively relieve the coarse grains and the weld line.
Acid etching additives in the acid etching process has the following main aspects: (1) Corrosion Inhibition: Due to the fast reaction between the F- and the natural oxide film and the aluminum matrix, and the reaction is severe, coarse grains and weld lines are prone to appear. Surface quality defects such as. In order to not only maintain a certain reaction speed but also not cause quality defects, organic compounds such as sodium citrate, sodium citrate, and glycerin are added to suppress the speed of acid etching and thus achieve corrosion inhibition. (2) Leveling effect: Extrusion profiles have a lot of slight marks, which are observed at high magnification under the peaks. Adding trisodium phosphate, diatomaceous earth, polyhydric alcohols and other compounds can protect the profile bottoms of the profiles. Flatten to achieve a leveling effect. (3) Promoting effect: The addition of accelerating agent can fully spread the acid etching additive into the bath, and effectively enter the inner layer of the surface of the aluminum substrate covered by the complex, so that the reaction can be continued so as not to cause uneven corrosion of the profile. (4) Surfactant action; adding surfactants such as sodium dodecyl benzene sulphonate, sodium lauryl sulphate and the like can further enhance the deoiling ability, and generate a layer of foam on the surface of the bath to suppress heat loss and troughs. Liquid volatilization, more important role is to increase the stability of the bath, because the negatively charged surfactant can be adsorbed around the particles, so that the particles produce electrostatic reaction force, so that the particles can be well suspended in the bath and not easy to precipitate . (5) Role of metal ions: Adding metal ions such as Cu2+ and Ag+ can prevent over-corrosion and make the effect of sand surface more delicate, uniform, and clear sand surface.
3, test
3.1 Test purpose
Through the acid etching and alkaline etching process test of aluminum profiles, the surface quality of the profiles obtained by the two processes and the amount of dissolved aluminum in the production process are compared.
In recent years, the production and sales volume of aluminum alloy matt profiles has been increasing, with a market share of over 80%. At present, the production of matt profiles generally uses alkaline etching methods, and the aluminum dissolved losses range from 3% to 5%, which results in huge waste of resources, greatly increases the difficulty of environmental protection management, and aggravates the “three wastes†processing burden of the company. Acid etching technology is developed for the lack of alkali etching methods, in principle, completely different from the alkaline pitting matt surface treatment. The process mainly adopts a unique method to generate a highly uniform and high-density molecular point corrosion on the surface of the aluminum profile, and by improving the material structure of the profile at the surface of the profile, thereby achieving the effect of smoothing the surface and eliminating the surface defects caused by the metallurgical process (for example, eliminating the extrusion Indentation, masking of the weld line, and mitigation of defects such as coarse grains, make the aluminum surface smooth and delicate, soft metallic luster, greatly improving the surface quality of aluminum profiles. With the acid-etched matt process, the aluminum melt loss is between 0.5% and 0.8%, which reduces the production cost to less than half of the traditional matt process, and the production efficiency has a substantial increase, which is of great practicality. Economic Value.
2, etching mechanism
Etching is chemical etching under certain conditions. The aluminum profile contacts the etching solution and reacts rapidly to form the complex in a very short time. The reaction equation is as follows:
3F-+A1-A1F3
6F-+A13+-A1.F63-
A1F63-+A12O3.3H2O-A13(OH)3F6+30H-
The resulting complex has a certain viscosity and easily adheres to the surface of the aluminum substrate to form a protective film. Extruded profiles generally have many slight marks. They are peaks observed under high power microscope. The protective film adhering to the aluminum matrix is ​​thicker in the recesses, thinner at the bulge, and has a greater chance of contact with the etching solution at the thin parts. , can continue to dissolve faster; thick areas are shielded by adherents to slow down the dope reaction rate, due to the difference in the rate of dissolution of the concave and convex parts, so as to achieve a smooth surface, eliminate extrusion marks (sand surface) Asia Light effect. Relieving coarse grain and weld line is directly related to the specific properties of acid etching. In the production of aluminum profiles, coarse grain and weld line are closely related to the die, extrusion process and the homogenization of the cast rod. The deeper the alkali etching, the more severe the coarse crystal and the weld line. Due to the fast acid etching time and short time, the reaction has ended without the occurrence of severe coarse grains and weld lines. Therefore, the acid etching process can effectively relieve the coarse grains and the weld line.
Acid etching additives in the acid etching process has the following main aspects: (1) Corrosion Inhibition: Due to the fast reaction between the F- and the natural oxide film and the aluminum matrix, and the reaction is severe, coarse grains and weld lines are prone to appear. Surface quality defects such as. In order to not only maintain a certain reaction speed but also not cause quality defects, organic compounds such as sodium citrate, sodium citrate, and glycerin are added to suppress the speed of acid etching and thus achieve corrosion inhibition. (2) Leveling effect: Extrusion profiles have a lot of slight marks, which are observed at high magnification under the peaks. Adding trisodium phosphate, diatomaceous earth, polyhydric alcohols and other compounds can protect the profile bottoms of the profiles. Flatten to achieve a leveling effect. (3) Promoting effect: The addition of accelerating agent can fully spread the acid etching additive into the bath, and effectively enter the inner layer of the surface of the aluminum substrate covered by the complex, so that the reaction can be continued so as not to cause uneven corrosion of the profile. (4) Surfactant action; adding surfactants such as sodium dodecyl benzene sulphonate, sodium lauryl sulphate and the like can further enhance the deoiling ability, and generate a layer of foam on the surface of the bath to suppress heat loss and troughs. Liquid volatilization, more important role is to increase the stability of the bath, because the negatively charged surfactant can be adsorbed around the particles, so that the particles produce electrostatic reaction force, so that the particles can be well suspended in the bath and not easy to precipitate . (5) Role of metal ions: Adding metal ions such as Cu2+ and Ag+ can prevent over-corrosion and make the effect of sand surface more delicate, uniform, and clear sand surface.
3, test
3.1 Test purpose
Through the acid etching and alkaline etching process test of aluminum profiles, the surface quality of the profiles obtained by the two processes and the amount of dissolved aluminum in the production process are compared.
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