The surface treatment of broken bridge aluminum profile is generally divided into six kinds: wood grain, fluorocarbon spraying, powder coated, baking varnish, electrostatic spray coating, coloring. Generally speaking the order of advantages and disadvantages: fluorocarbon spraying ＞ electrostatic spray coating ＞ powder coating ＞ wood grain ＞ coloring ＞ baking varnish. Of course there are very few processes that are very strong, while there are sometimes combinations of each other.
Ⅰ Wood Grain
One kind: through the heat transfer film or paper, the pattern printed on the transfer film to the profile above. Generally the profile first pickling (so that the base color is easy to adhere to the surface of the profile) and then sprayed on the profile of wood grain powder, in the film when the air inside the extraction, in the 190° - 200° oven baking, ink is heat sublimation to the coating. There are cherry, teak, yellow purlin, white oak and other textures. This image is realistic, but poor weather resistance.
Another kind: the surface of the profile is coated with wood grain primer for curing, and then a brush pattern machine is used to roll the wood grain on the coating to form the curing. This kind of process profile has a strong sense of concavity and convexity, good weather resistance, but the pattern is not vivid enough.
Ⅱ Electrostatic Spray Coating - Powder Coating
Generally powder coating uses polyurethane, polyurethane resin, epoxy resin, hydroxy polyester resin, epoxy polyester resin as raw materials. Electrostatic spray coating is generally in the powder spraying before the profile surface should be acid washing, through the electrostatic spray coating machine to spray powder coating to the surface of the profile, in the electrostatic effect, the powder will be uniformly adsorbed on the surface of the profile, the formation of powde coating. This coating is generally more than 30 microns.
Advantages: corrosion resistance, weather resistance, impact resistance, abrasion resistance, can be subjected to long-term ultraviolet radiation and acid rain erosion without coating chalking, fading, peeling, phenomenon.
Disadvantages: long-term ultraviolet radiation, will be illuminated into the natural color fading, indoor and outdoor appear obvious color difference (generally 2 years to 3 years time).
Ⅲ Electrostatic Spray Coating - Fluorocarbon Spraying (Liquid Spraying)
Fluorocarbon spraying is a polyvinylidene fluoride resin nCH2CF2 grill (CH2CF2) n (PVDF) as the base material or with metal aluminum powder (with pearlescent will be sparkling, very expensive, at first glance is a good deal) for the color of the paint produced. Because the base material of fluorocarbon is fluorine/carbon is chemical short chain nature, this and H2 ions combined with the most stable.
Process: pre-treatment process: de-oiled and decontaminated aluminum → washing → alkali washing (degreasing) → washing → acid washing → wahsing → chrome → washing → pure water washing
Spraying process: spraying primer → top coat → overcoat varnish → baking (180-250℃) → quality control
Multi-layer spraying process to three times spraying (spraying primer, top coat, varnish paint) and secondary spraying (primer, top coat). The general coating is above 40-60 microns.
Advantages: stable chemical structure, abrasion resistance, impact resistance, corrosion resistance, frost resistance, crack resistance. Can withstand UV radiation for a long time and at the same time has a stronger resistance to fading than powder coating, similar to automotive surface paint. High-end materials have self-cleaning properties, scrub resistance.
Disadvantages: metal surface liquid coating by liquid paint and compressed air in the water has a greater impact (electrostatic liquid change principle), so electrostatic spraying liquid there is a surface instability, small manufacturers are difficult to deal with this process.
Need to use high-voltage electrostatic electrical spray gun, because the fluorocarbon coating made by unsuitable equipment, will be uneven color, surface shadows, the coating is not firm problem.
Ⅳ Baking Varnish
It can customize the color, can be made according to customer demand for similar colors.
Process: first sand the substrate to a certain degree of roughness, in the spray bottom adhesion agent, and then spray paint, after 140°-180° high temperature baking fixed.
Advantages: better color development.
Disadvantages: high requirements for the paint.
Ⅴ Coloring - (Chemical Coloring, Electrolytic Coloring)
① Chemical coloring: chemical coloring is after anodic oxidation of the profile impregnated in solution, the dye molecules into the porous layer of the oxide film, so that show color out.
Disadvantages: the sunlight resistance and weather resistance of the coloring film are not as good as electrolytic coloring.
② Electrolytic coloring: Electrolytic coloring is in a solution containing metal ions, through the action of electric current metal ions reduced to metal (or metal oxide) deposited on the bottom of the oxide film, due to the scattering of light presents a different color, of course, can also be without coloring, maintaining the original color (silver oxide). Initially, electrolytic coloring is done with tin salts and tin-nickel salts to produce champagne and black colors. Bronze colors are produced by changing the voltage or coloring time. Colors include (champagne, bronze, coffee, antique bronze).
Now slowly switching from using tin-nickel salts to single tin salts. Nickel salt is in the whole system is mainly competitive reduction, increase the precipitation of tin salt, change the color tone, the presence of nickel salt can make the black reddish. Because nickel is a pollutant, is also slowly using coloring stabilizers to replace nickel, while making single tin salt and tin-nickel salt performance stability, single tin salt is the future trend.
Sealing holes: 6063 and 6061 of the series is suitable for extrusion oxidation and coloring, 7005 is more difficult to color. The oxide film generated by monosulfate oxidation is porous, with a hole (like a nut) right in the middle of the hexagonal structure. Tin particles generated by the reduction of tin salts by pitting are deposited in the micropores, and colors are produced due to light diffraction. However, a structure full of voids is not corrosion-resistant and needs to be sealed.
Now there are room temperature (old process: nickel + fluorine new process: potassium hexafluorozirconate), medium-temperature, high-temperature sealing (steam sealing).
At present, the medium-temperature sealing holes are used more, medium-temperature sealing holes are divided into nickel-free and fluorine-free (with alkali metals and alkaline earth metals) and nickel sealing holes (nickel acetate), generated by the hydrate will be sealed pores, sealing the corrosion resistance is greatly improved.
Ⅵ Electrophoretic coating
Electrophoretic coating is divided into glossy electrophoresis and matte electrophoresis, and can also be divided into varnish and color paint. Varnish is the most common, and color paint (matte paint, white paint, color paint).
Electrophoretic coating is the electrophoretic treatment after anodizing. And aluminum profile electrophoresis refers to the process of forming a dense resin film layer on the surface of the aluminum profile after it is placed in the electrophoresis tank and passed through the electric current. The film layer is a composite coating of anodic oxide film + electrophoretic coating, and his weather resistance is stronger than that of anodic oxide profiles.
Electrophoresis profiles have a gorgeous appearance, but the film layer is easy to scratch.
Electrophoretic coating is different from electrolytic coloring, that is, spot coloring applies the sealing process, while electrophoretic coating applies the electrophoretic coating process. The electrophoretic coating of aluminum profile mainly uses acrylic resin, with organic amine or inorganic alkali as neutralizer, melamine formaldehyde resin as curing agent, with pigment + solvent + additive components.
Advantages:
① The coating is plump, even, flat and smooth; paint film hardness, adhesion, corrosion resistance, acid and alkali resistance, impact resistance;
② Stronger penetration resistance than other surface treatment processes, not easy to fade; electrophoretic painting requires smooth surface of aluminum alloy and few mechanical defects;
③ Strict requirements for oxidation coloring process;
Disadvantages: single color only bronze (silver-white, champagne, golden yellow, black, imitation stainless steel color and other colors), tiny defects of profiles are easy to find, electrophoretic color is easy to produce color difference.
Matting Electrophoresis
Matting electrophoresis, also known as ceramic electrophoresis, is considered to be an enhanced version of electrophoresis. It has a silkier feel than powder coating and reduces the orange peel of aluminum profiles to a certain extent.
Advantages:
① The surface hardness of the aluminum profiles with porcelain coating is high, corrosion-resistant, weather-resistant, and salt spray-resistant;
② The surface is softer, which can reduce the indoor reflective pollution because of the profile;
③ Silky smooth feel;
④ Easy to clean, there are stains on the surface as long as the surface can be removed by gently wiping.
Note: It is recommended to use water-based paint is more environmentally friendly.
