Surface treatment: it is through mechanical and chemical methods of treatment, can form a layer of protection on the surface of the product to protect the body of the protective layer. It can reach a stable state in nature, increase the corrosion resistance of the body and increase the beauty of the product, thus enhancing the value of the product. The choice of surface treatment type should first from the use of the environment, service life, human appreciation of the point of view, of course, the economic value is also the core of the consideration.
The process of surface treatment includes pre-treatment, film forming, post-film treatment. Packaging, warehousing. Shipments and other processes, including pre-treatment including mechanical treatment, chemical treatment.
Mechanical treatment includes noisy spraying, shot blasting, grinding, polishing, waxing and other processes. Mechanical treatment aims to make the product surface to eliminate unevenness, remedying the surface of other bad appearance. Chemical treatment to make the product surface oil stains and rust removal, industrial aluminum profile and the formation of a layer of film-forming substances can make a better combination or and into the active metal body, to ensure that the plating layer has a stable state, increase the bonding force of the protective layer, so as to achieve the role of the protection of the body.
Aluminum surface treatment
Aluminum common chemical treatment of chroming, painting, electroplating, anodic oxidation, electrophoresis and other processes. Mechanical treatment includes brushing, polishing, noisy spraying, sanding and other processes.
Industrial aluminum profiles
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Section 1: Chroming
Chroming will form a chemical conversion film on the surface of the product. Chromating will form a layer of chemical conversion film on the surface of the product, the thickness of the film is 0.5-4um, this layer of conversion film has good adsorption, and is mainly used as a coating base layer. The appearance of golden yellow, aluminum color, green, etc.. This kind of conversion film has good conductivity and is the best option for electronic products, such as the conductive strip inside the cell phone battery, magnetic devices and so on. This film is suitable for all aluminum and aluminum alloy products. However, this conversion film is soft and not wear-resistant, so it is not good for making products outside parts to utilize.
Chromating process:
Degreasing->Alumina->Chromating->Packaging->Storage
Chromating is suitable for aluminum and aluminum alloys, magnesium and magnesium alloys products.
Quality Requirements:
1) Uniform color, film layer is meticulous, there can be no bumps, scratches, touching with hands, there can be no roughness, fall off the gray and other phenomena.
2 ) Membrane thickness 0.3-4um .
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Section 2, anodic oxidation
Anodic oxidation: can make the product surface form a layer of uniform, dense Oxide layer, (Al2O3.6H2O commonly known as steel jade) this film can make the surface hardness of the product (200-300HV), if the special products can be done hard anodic oxidation, the surface hardness of the product can be up to 400-1200HV, so the hard anodic oxidation is a cylinder, transmission, the indispensable surface treatment process.
Additionally, this kind of product has very good abrasion resistance, and can be used for aviation and aerospace related products. Anodic oxidation and hard anodic oxidation difference: anodic oxidation can be colored workbench, decorative than hard oxidation is much better. Construction points: anodic oxidation of the material requirements are very strict, different materials have different decorative effect on the surface, commonly used materials are 6061, 6063, 7075, 2024, etc., of which, the relative effect of 2024 is a little worse, due to the different content of CU in the material, so 7075 hard oxidation is yellow, 6061, 6063 brown, but the ordinary anodized 6061, 6063, 7075 not much. 6063, 7075 not much difference, but 2024 is easy to appear a lot of gold spots.
A common process
Common anodic oxidation process is brushed matte color, brushed glossy color, brushed glossy dyeing, matte brushed dyeing (can be dyed into any color). Polished glossy natural color, polished matte natural color, polished glossy dyeing, polished matte dyeing. Spray noisy glossy natural color, spray noisy matte natural color, sandblasted dyeing. All of the above plating types can be used in lighting equipment.
Two, anodic oxidation process
Degreasing-> alkali etching-> chemical throw-> neutralization-> Lidi-> neutralization
Anodic Oxidation->Dyeing->Sealing->Hot water washing->Drying
Three, common quality anomalies to judge
A The surface appears to be splotchy. This abnormality is generally due to poor metal tempering or the material itself is too poor to deal with, re-heat treatment. Or replace the material.
B Rainbow color on the surface. This abnormality is generally caused by anode operation errors. The anode is loose when it is hung up, resulting in poor conductivity of the product.
C, the surface bruises, scratches serious. This kind of abnormality is generally due to transportation or processing, the operation is caused by carelessness, the treatment method, the power back, polished and then electricity.
D, white spots appear on the surface when dyeing. This abnormality is generally due to anode operation, oil in the water, or other impurities.
Four, quality standards
1) film thickness of 5-25um, hardness of 200HV or more, sealing test color change rate of less than 5%
2) salt spray test in 36 hours or more, and can achieve more than 9 levels of CNS standards
3) the appearance of the phenomenon can not have bruises, scratches, color clouds and so on. The surface can not have hanging points, yellowing and other bad phenomena
Four, die-casting aluminum, such as A380, A365, A382, etc. can not do anodic oxidation
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Section III, aluminum plating process
One, the advantages of aluminum and aluminum alloy materials
With good electrical conductivity, fast heat transfer, light weight, easy to form and other advantages, but aluminum and aluminum alloy has a low hardness, not wear-resistant, prone to inter-crystalline corrosion, not easy to weld, and other shortcomings, which affects the scope of use. Therefore, in order to avoid the shortcomings, modern industry, the use of electroplating to solve this problem.
Two, the advantages of aluminum plating
1) improve decorative,
2) improve surface hardness and wear resistance
3) reduce the coefficient of friction, improve lubrication.
4 ） Improve surface conductivity.
5 ） Improve corrosion resistance (including combinations with other metals)
6 ） Easy to weld
7 ） Improve the bonding force when hot pressing with rubber.
8 ） Improve reflectivity
9 ） Repair dimensional tolerances
Because aluminum is a more active metal, the plated material are more active than the aluminum, therefore, before plating, it must do the corresponding chemical transformation, such as zinc immersion, zinc-iron alloy, zinc-nickel alloy, and the zinc and zinc alloy substrate has a good combination of intermediate layer of cyanide copper-plated layer. Die-casting aluminum due to the loose structure of the body, grinding, can not be polished off the body surface part, otherwise pinholes, spit acid, peeling and other phenomena.
Three, aluminum plating process
Degreasing - > alkaline etching - > activation - > zinc replacement - > activation - > plating (such as nickel, zinc, copper, etc.) - >. copper, etc.) ->Chrome plating or passivation ->Drying.
1, common aluminum plating plating types are
Nickel plating (pearl nickel, sand nickel, black nickel), silver plating (face silver, thick silver), gold plating, zinc plating (color zinc, black zinc, blue zinc), copper plating (bronze drum copper, white tin copper, alkaline copper, burnt copper, acid copper), chrome plating (white chrome, hard chrome, black chrome) and so on.
2, the use of common plating
1) black plating, such as black zinc, black nickel, etc. are used in optical electronics and medical equipment.
2 ） Gold plating, silver is the best conductor of electronic products, but also to improve the product's higher decorative, but the price is more expensive, are generally used in electronic products conductive, such as high-precision wire terminals and other plating.
3 ） Copper, nickel, chromium is the most popular mixed plating in the field of modern science, regardless of decorative, corrosion resistance, are currently the world's most popular plating. Low price, available in sports equipment, lighting, most of the electronics industry.
4 ） Copper plating, white tin copper is developed in the 70s and 80s for environmentally friendly form of plating, bright white, is the first choice of the jewelry industry. Bronze (lead tin copper can be made to imitate gold, so it is a better decorative plating), but the copper anti-color is relatively poor, so the development is relatively slow.
5 ） Zinc plating: zinc plating is greenish-white, easily soluble in acids and alkalis. Since the standard potential of zinc is more negative than iron, it provides reliable electrochemical protection for steel. Zinc can be chosen as a protective layer for steel products used in industrial and marine atmospheres.
6) hard chromium, chromium plating deposited under certain conditions has a high hardness and wear resistance, hardness to HV900-1200kg/mm, chromium is commonly used plating in the highest hardness of the plating can improve the wear resistance of the parts, prolong the service life. Such as work, mold, measurement, clamps, and so on. Therefore the plating is cylinder, hydraulic, transmission system indispensable treatment.
3, common abnormalities and improvement measures
1) stripping: a zinc replacement is not good, too long or too short, improvement measures, re-determine the replacement time, bath temperature, bath concentration and other operating parameters.
b , activation is not enough, improvement measures, change the activation mode.
c pre-treatment is not complete, the surface of the workpiece has oil, improvement measures, strengthen the pre-treatment.
2 ） Surface roughness: a, plating solution light agent, softener, pinhole dose is not suitable, readjust the number of additives.
b The surface of the body itself is rough, re-polished and then plated.
3 ） Surface yellowing is low-potential alignment is not correct, change the way to mount. Add the appropriate amount of alignment agent.
4 ） Surface hairy teeth: plating solution is too dirty, strengthen the filtration, make appropriate tank treatment.
4, quality requirements
1) The appearance of no yellowing, pinholes, burrs, blisters, bruises, scratches and other bad phenomena.
2) Film thickness of 15um or more, salt spray test 48 hours, up to the U.S. military standard 9 or more, the potential difference of 130-150mv area.
3 ） The bonding force can pass the 60 degree bending test.
4 ） The products in special environment can be changed accordingly.
5, aluminum and aluminum alloy plating operation precautions
1) Aluminum parts plating should be used as aluminum alloy hangers;
2) Aluminum and aluminum alloy after the immersion of the processes must be carried out quickly, the shorter the interval between the processes of the cabinet aluminum profiles as good as possible, so as not to re-oxidize;
3) The second time of zinc immersion should not be too long, so as not to cause over-erosion
4 ） The water washing must be clean;
5 ） The electroplating process should be prevented from power failure in the middle of the process.
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Section IV, aluminum coating
Coating is divided into dip coating, spraying, spraying, rolling and brushing, etc., which is mainly dip coating and spraying. Dip coating and spraying mainly, dip coating is also known as electrophoretic coating, which uses electrochemical methods of organic resin particles deposited on the surface of the workpiece to form a transparent or a variety of colors of the organic coating. Among them, cathodic electrophoresis is a new process developed in the seventies and is the main process in the dip coating industry. Advantages of good corrosion resistance, strong anti-color change performance, good bonding characteristics. Spraying is divided into powder coating and liquid coating, of which electrostatic coating is the more popular process in the industry.
One, the scope of the coating process
Because of good corrosion resistance, low price, color (can do any different colors) it is suitable for all aluminum materials, but the material structure is too loose, such as sand products, need to scrape the gray work, the relative quality should be poorer.
1, the working principle of electrostatic painting
Under the action of the pump, so that the paint into the electric field, the paint particles are negatively charged. Under the action of atomizing air pressure, the paint becomes finer and more uniform then under the action of working air pressure, the paint is evenly sprayed on the surface of the workpiece under the action of spinning cup or nozzle. As in the same vertical plane, the distance between the spray gun and the workpiece is equal, the same interface electric field strength is also the same, so the positive and negative charges are attracted to each other, and the surface of the workpiece is coated with a layer of uniform organic resin coating. Then under the condition of high temperature baking, the resin reaches the state of leveling and curing. It is firmly set on the surface of the workpiece to protect the workpiece.
2, aluminum coating process
Mechanical grinding - > degreasing - > in addition to the oxide film - > chrome - > spray powder or liquid - > baking -&>Hanging->Full inspection->Packaging->Storage
1) Powder and liquid operations common abnormalities and treatment
Section V, aluminum chemical plating
A, the principle of chemical plating
Principle of chemical plating
Principle of chemical plating < /p>
Chemical plating is in the absence of current through (no external power) with the help of reducing agent in the same solution of redox, so that the metal ions reductive deposition on the surface of the parts of a plating method. Therefore, chemical plating can be described as a deposition of metal, controllable, self-catalyzed chemical reduction process, the reaction formula is:
Two, chemical plating characteristics
With the development of industry, chemical plating has become a promising technology, with other plating methods, chemical plating has the following characteristics:
1) can be used in a variety of materials such as metals, semiconductors and non-conductors.
1) It can coat metal on parts made of metal, semiconductors and non-conductors.
2 ） Regardless of the complexity of the geometry of the part, wherever it can touch the solution can be obtained with a uniform thickness of the coating.
3 ) For self-catalyzed chemical plating, it is possible to obtain larger thicknesses of plating, and even electroforming.
4 ) No current is required.
5 ) The plating layer is dense and less porous.
6 ） The coating often has special chemical and mechanical properties.
Because of the many advantages of chemical plating, chemical plating more and more in the industry, the electronics industry in the development of faster. The following chemical nickel plating as an example to do the following introduction:
1) chemical nickel plating due to the use of sodium hypophosphite as a reductant, so generally obtained for the plating of nickel-phosphorus alloy. According to the different phosphorus content can be divided into low phosphorus (1% -4%) in the phosphorus (4% -10%) and high phosphorus (10% -12%). From different PH value of the plating solution can be obtained from different phosphorus content of the plating layer, in the PH = 4-5, can be obtained in the phosphorus and high phosphorus alloy. Low-phosphorus and medium-phosphorus alloys can be obtained from weakly alkaline solutions at pH=8-10. NI-P alloys containing more than 8% phosphorus are amorphous coatings with particularly good corrosion resistance due to the absence of grain boundaries. Through heat treatment 300-400 degrees into a mixture of amorphous and crystalline hardness of up to HV = 1150, chemical plating heat treatment hardness close to the hardness of hard chrome, is the ideal alternative to hard chrome layer plating, but also in the application of aluminum on the good plating (can be suitable for all aluminum and aluminum alloy products, including forging, die casting, aluminum profiles, etc.). Disadvantage: The plating is brittle, but the plasticity of the product is greatly improved after heat treatment. (Generally more than 400 degrees of heat treatment for four hours, its plasticity to improve a lot)
2) Aluminum chemical nickel plating process:
Ultrasonic degreasing-> remove oxide film-> the first zinc replacement-> and chemical ->Second zinc replacement ->Chemical nickel plating ->Passivation ->Ultrasonic cleaning ->Baking ->Full inspection -&>Packaging
3) Unqualified plating of the removal:
Steel, aluminum, copper, plastic and other chemical nickel layer can be used to remove concentrated nitric acid. But the parts should be dried into the tank, if the moisture will lead to excessive corrosion of the base metal. The working temperature is below 35 degrees.
4 ） Quality requirements:
a, film thickness in the 5-30um range
b, salt spray test to more than 24 hours, up to CNS standard 9 or more.
c, through the 60 degree bending test, no peeling phenomenon
d, the appearance of no bruises, scratches, water stains and other bad phenomena.
e, the film is uniform, there can be no fog, white spots, dew plating phenomenon
Section VI, the plating conditions of classification and selection
From the corrosion requirements, the design of the surface treatment should be done as follows:
1) Precious metals (gold, platinum), stainless steel containing chromium in more than 18%, magnetic alloy materials, as well as nickel-copper alloys, and so on, generally do not need to add a protective layer. need to add another protective layer.
2) Carbon steel, low alloy steel and cast iron parts, easy to corrode in the atmosphere, should be added to the protective layer.
3) Copper and copper alloy parts, according to different conditions of use, using bright pickling, passivation, electroplating or painting protection. Precision parts made of phosphor bronze or beryllium bronze can be made without surface treatment.
4) Parts made of aluminum and aluminum alloy can be anodized and closed treatment. Small parts that are not suitable for anodic oxidation can be treated with chemical oxidation. Casting aluminum alloy can be protected by painting.
5) Parts made of zinc alloy can be protected by phosphating, passivation, electroplating or painting.
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Section VII. Plasma Surface Treatment
A plasma surface treatment machine is used to carry out certain physicochemical modifications to the metal coated cardboard to improve the surface adhesion so that it can be bonded as easily as ordinary paper. The use of conventional water-based cold glue can make the laminating or varnishing cardboard in the gluing machine to get a reliable bond, no longer need to partial laminating, partial varnishing, surface sanding and cutting line and other processes, and also no longer need to be replaced because of the different cardboard and different special glue.
Through the plasma surface treatment, not only can enhance the applicability of the metal coated cardboard to the glue, no longer rely on special glue to achieve high quality bonding. Moreover, it improves the spreading performance of the surface and prevents the generation of air bubbles. The most important thing about the plasma surface treatment equipment of Shanghai Xuanyi Instrument Co., Ltd. is that after the atmospheric pressure plasma treatment, it can let the carton manufacturer get the high-grade products with more guaranteed quality at lower cost and higher efficiency.
Metal coated cardboard plasma surface treatment equipment plasma plasma cleaner product features:
1, laminated folding carton adhesive firmness, can use environmentally friendly water-based adhesives, reducing the amount of glue used, effectively reducing production costs.
2, in the normal process settings under the treatment, the surface will not find any traces of treatment. Plasma close to room temperature, it will not produce any thermal effect on the surface.
3, in the need to deal with double-sided or multi-side of the box, the system may be configured with a different number of guns to complete the pre-treatment work.
4, the plasma itself is electrically neutral, in the treatment of aluminum surface will not burn the surface.
5, the product can run continuously with high efficiency, fast processing speed, reliable bonding, low cost and other advantages.
6, can adjust the plasma power, processing distance, cleaning speed for quality control.
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Section VIII. Electrophoretic treatment of aluminum
Color electrophoretic coating of aluminum is a novel surface treatment process. It uses electrochemical methods to deposit colloidal particles of organic resin on the part, forming an organic coating layer of transparent or various colors. According to the different charged condition of the resin particles in the electrophoretic paint after ionization, it can be divided into anodic electrophoresis (the resin particles become negative ions after ionization) and cathodic electrophoresis (the resin particles become positive ions after ionization).
The corrosion resistance of electrophoretic coating layer is extremely good (it can pass neutral salt spray test for more than 400 hours), and it has strong resistance to discoloration; it has good bonding force with base metal, and it can be subjected to various kinds of mechanical processing; the coating layer has bright colors, and it can be formulated into various colors according to the requirements of users, and the common ones are gold, coffee, gunmetal, black, etc.; it has good performance in construction, and has less pollution and harm to the environment compared with the paints. It has better construction performance than paint and less pollution and harm to the environment. Therefore, it is used in automobile shells and various accessories, bicycle handlebars and accessories, various daily-use small hardware accessories, furniture, handicrafts and so on. Since cathodic electrophoresis is more advanced, here we take cathodic electrophoresis as the main subject of our introduction;
Cathodic electrophoresis coating is a complex electrochemical and colloid chemical process. Electrophoretic paint itself is a colloidal and suspension multi-component system, there are two components of diffuse phase (resin, pigment particles) and continuous phase (water). Four processes of cathodic electrophoresis:
1. Electrophoresis Positively charged water-soluble resin particles and their adsorbed pigments move toward the cathode.
2. Electrodeposition Positively charged resin particles arrive at the surface of the part (cathode) and discharge, forming a water-insoluble deposition layer, which forms a paint film after baking.
3, electrodeposition of water from the sedimentary layer precipitation, when the water content drops to 5% -15%, can be baked.
4, electrolysis of water by direct current electrolysis, release hydrogen and oxygen, due to electrolysis leads to a decrease in penetration, affecting the appearance of the paint film, reduce the adhesion of the paint film, increase power consumption, therefore, weakening the electrolysis of water is very necessary.
The process of electrophoresis:
Degreasing-> removal of oxidized skin-> chroming-> electrophoresis-> drying-> packaging
V. Quality standard
1) No color difference, orange peel, pinhole, rainbow, bruise, scratch and other abnormalities in appearance
2) The film thickness is 40-60um, the salt spray test is more than 400 hours, and it has passed the level 9 of CNS standard
3) The film can pass the 60-degree bending test without peeling off the skin phenomenon
4) The hundred-figure test and the ball drop test can reach the national standard
5) The film can pass the national standard. national standard