048 (2)

What kind of quality inspection is usually required for color-coated sheets to meet the standards?

Color-coated panels require 48 inspection procedures in 5 categories. So, what are the 5 categories and 48 inspection procedures? Usually, from raw materials entering the factory to finished products leaving the factory, the category refers to the inspection of the substrate from entering the factory to before going online: mainly including thickness, width and other appearance quality and material, Coating adhesion, coating weight and other internal quality testing. The second category refers to the testing of coatings from entering the factory to before going online: mainly including the color difference, gloss and basic performance testing of the samples shipped with the goods.

The second type refers to the online detection of the substrate: mainly including board type and board surface inspection, such as whether there are defects such as wave edges, loose edges, bulges, plate patterns, zinc, zinc lines, and whether they are oxidized and blackened, etc. The fourth type refers to coating On-line inspection of layers: mainly includes color difference, gloss, coating thickness, coating uniformity, etc., and at the same time, it is necessary to monitor whether there are appearance defects such as scratches, pressure pits, missing coatings, and waste that affect the use. The fifth category is color coating The most critical part of board quality inspection is the performance inspection of the color-coated product itself, which mainly includes the tests of coating adhesion, coating hardness, solvent resistance, corrosion resistance, and aging resistance. Due to the limitation of the detection complexity and the long detection time, it is generally carried out by sampling detection. In addition to the aging resistance and corrosion resistance which belong to the random inspection items, all the above-mentioned inspections, each coil will have detailed records, and will be recorded in detail in the product quality documents by the quality inspectors for future inspection. HUNGTHAI metal’s color-coated panels Strictly implement the national standard, each product goes through 5 categories and 48 inspection procedures to ensure that each product leaves the factory with zero defects.

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How to reduce the rate of aging of galvanized sheet

The galvanized sheet may be aged if it is used for too long or not used for a long time. Why do you say that? Long-term construction or storage will inevitably expose to sunlight. After long-term light exposure, aging will occur, which is inevitable, but we can prevent and reduce the aging speed in advance, so what should we do?

A necessary condition for the aging or photochemical reaction of the color-coated board is that the surface components of the color-coated board can absorb radiant energy. Secondly, when the radiation energy absorbed by the molecules is greater than the bond energy of the molecules, the coating of the color-coated board will degrade. The shorter the wavelength of light, the more energy it contains.

According to the above theory, the aging of the color-coated board in the atmospheric environment is that the ultraviolet light band energy absorbed by the coating molecules is higher than the molecular bond energy in the sunlight, resulting in the degradation of the coating molecules. With the aging of the coating film, the body of the substrate is gradually lost, and the surface of the coating gradually becomes rough and loses its luster. The loss of binder eventually leaves stable pigment particles that remain on the surface of the coating film as an unbound powder, a process called pulverization.

To sum up, the aging resistance of polyester color-coated boards with different coating thicknesses varies greatly, the aging resistance of thin-coated color-coated boards is poor, and the aging resistance of ordinary coating thicknesses is relatively good.

Furthermore, it is not feasible to reduce the production cost of color-coated sheets by thinning the coating, which will inevitably bring about serious quality problems. At the same time, it is also demonstrated from the side that it is necessary to clearly indicate the coating thickness in the order contract of foreign color-coated sheet importers.

With the development of my country’s construction industry, the related building materials industry has a broader space for development. Galvanized sheet has been recognized by many users in the market for its unique advantages.

Galvanized steel sheet is cold rolled or hot rolled, and the slender steel sheet is coated with a layer of zinc of varying thickness. The production of galvanized sheet concentrates the advantages of galvanized sheet and strip, so that the product is not only corrosion-resistant and beautiful, but also has high dimensional accuracy, good surface quality, easy processing and material saving. To a certain extent, the products can meet the needs of the public and better meet the needs of users.

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Color selection and application advantages of color coated steel plate

Color steel plate is a steel plate produced after a series of treatments on a continuous line, such as cold-rolled strip. When designing the plates, HUNGTHAI will make various colors according to the needs of customers. Color selection of color steel plate coating: The color selection mainly considers the degree of matching between the user’s preference and the surrounding environment. However, from an application technology point of view, the choice of light-colored paints is larger. Inorganic pigments with better durability can be selected. In addition, the paint has strong heat reflection ability, and the temperature of the paint itself is lower in summer, which is beneficial to improve the service life of the paint.

Even if the color steel coating is discolored or chalked, the contrast between the light-colored film and the original color after the change is small, and the appearance has little effect. Dark colors are mostly organic. It can easily fade and discolor in as little as three months if exposed to UV radiation. For color-coated steel sheets, the thermal expansion coefficients of the coating and the steel sheet are usually different, especially the linear expansion coefficients of the metal matrix and the organic coating are quite different. When the ambient temperature changes, the bonding interface between the substrate and the coating will generate expansion or contraction stress, and if it cannot be properly released, coating cracks will occur.

Color steel plate is actually a kind of steel plate with special organic coating. Due to its excellent performance, it is widely used in construction, home appliances, transportation and other industries. What are the advantages of the color steel plate we often use? Let’s look at it from a few aspects:

  1. Since many building structures have seismic problems, in order to make them have better seismic performance, color steel plates can be used. The structural system has strong seismic resistance and anti-horizontal load capacity, and is suitable for areas with seismic intensity above 8 degrees.
  2. Wind resistance, color steel structure has the advantages of light weight, high strength, good overall rigidity and strong deformation ability.
  3. Durability, the color steel plate residential structure has a long service life compared with ordinary houses.
  4. The thermal insulation material for thermal insulation color steel plate is mainly made of glass fiber wool, which has a good thermal insulation effect.
  5. Sound insulation, sound insulation effect is an important indicator for evaluating residential buildings. The windows installed with color steel and light steel systems use insulating glass, which has good sound insulation effect.
  6. Comfort, the color steel plate wall adopts a high-efficiency energy-saving system, which has a breathing function and can adjust the drying and humidity of the indoor air; the roof has a ventilation function, which can form a flowing air room above the house to ensure the ventilation and heat dissipation requirements inside the roof.
  7. Environmental protection, color steel materials can be recycled to achieve green and pollution-free.
  8. Energy saving, all use high-efficiency energy-saving walls, which have good thermal insulation, heat insulation and sound insulation effects, and can reach 50% energy saving standards.
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Selection of coating materials for color steel coils

At present, the types of coatings used for color-coated steel plates include polyester coatings (PE), fluorocarbon coatings (PVDF), silicon modified coatings (SMP), high weather resistance coatings (HDP), acrylic coatings, polyurethane coatings (PU), plastic Sol paint (PVC), etc.

  1. The polyester coating has good adhesion to the material. The color-coated steel plate is easy to process and form, the price is low, the product is many, and the color choice is large. Under direct exposure in general environment, the anti-corrosion life can be as long as 7-8 years. However, in industrial environments or heavily polluted areas, its service life will be relatively shortened. However, the UV resistance and film crush resistance of polyester coatings are not ideal. Therefore, the use of PE coatings still needs to be restricted. It is typically used in areas with less air pollution or products that require multiple molding and processing.
  2. Since polyester contains active groups -OH/-COOH, it is easy to react with other macromolecules and polymers. In order to improve the light resistance and pulverization of PE, silicone resin with excellent color retention and heat resistance is used for denaturation reaction, and the denaturation rate with PE can be between 5% and 50%. SMP provides better durability of steel plates, and its anti-corrosion life can reach 10-12 years. Of course, its price is also higher than that of PE, but due to the unsatisfactory adhesion of silicone resin to the material and the formability of processing, SMP color-coated steel plate is not suitable for occasions requiring multiple forming processes, and most of them are used for building roofs and exterior walls.
  3. The high weather resistance polyester coating is better than the ordinary silicon modified polyester coating, and the outdoor weather resistance is up to 15 years. In the process of synthesizing polyester resin with high weather resistance, monomers containing cyclohexane structure are used to achieve a balance between resin flexibility, weather resistance and cost. Aromatic polyols and polyacids are used to reduce the UV absorption of the resin and achieve high weather resistance of the coating. Add UV absorbers and steric blocking amines (HALS) to paint formulations to improve the weatherability of the paint film.

Fourth, the plastisol has good water resistance and chemical resistance. It is generally a high solid content coating with a coating thickness of 100-300 μM, which can provide a smooth PVC coating or a light embossing treatment as an embossed coating; since the PVC coating is a thermoplastic resin with a high film thickness, Therefore, it can provide good protection for the steel plate. But PVC has poor heat resistance.

  1. Due to the strong bond energy between PVDF chemical bonds, the coating has good corrosion resistance and color retention. It is a more advanced product in Baosteel’s color steel coil coatings for construction, with large molecular weight and direct bonding structure. Therefore, in addition to chemical resistance, its mechanical properties, UV resistance and heat resistance are also outstanding. Under normal circumstances, the anti-corrosion life can be as long as 20-25 years. In recent years, fluororesins copolymerized with chlorotrifluoroethylene and vinyl ester monomers have been widely used in my country, and are widely used in building exterior walls and metal panels. Due to the use of easily hydrolyzed vinyl ester monomers, the fluorine content is about 30% lower than that of PVDF, and its weather resistance has a certain gap with PVDF.
  2. Acrylic resin has good comprehensive performance and high price, and is only used in specific fields (such as containers).
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Maintenance of Color Coated Steel Coils

While factory pre-painted architectural panels last many years longer than regular painted panels, they still require thorough cleaning. If there is automatic washing of rainwater, such as roof slabs, no maintenance is required. Cleaning can remove accumulated corrosion and keep the building looking good without the need for painting. Places that need to be cleaned include brackets, side panels under drip eaves, warehouse door panels, grooves on the back of drip eaves, etc.

(1) Cleaning: Usually, most of the dust and residue accumulated on the surface of the steel plate can be removed with clean water. In theory, cleaning should be done at least every six months. More frequent cleaning should be done in coastal areas with more salt spray and in places with more industrial dust. For stubborn stains that cannot be washed off, use a weak detergent or household ammonia. In any case, before cleaning a large area, scrub in inconspicuous small pieces. Take a scoop of laundry detergent (or other detergent with less than 0.5% phosphate) and dissolve it in 5 gallons of hot water; or dissolve a cup of household ammonia in 5 gallons of room temperature water. Do not mix ammonia with any bleach; do not mix detergent and bleach without permission. If cleaning and bleaching is required, use a detergent that contains bleach. Using any of the above cleaners, clean the steel surface from top to bottom with a soft soaked cloth, sponge, soft brush or low pressure nozzle to avoid streaks and bright spots. Stain removal powders or industrial detergents are not recommended as they can damage the paint. Water-soluble detergents are effective and can be used. If fungus and mold cannot be removed by the above methods, a detergent containing bleach is recommended. After cleaning, the surface of the steel plate should be completely free of cleaning agent residues.

(2) Repainting: If scratches appear during installation and use, it may be necessary to repaint the defective parts. Improper or excessive patching can damage the entire surface. Scratches that are not apparent at 6 feet should not be repaired, as they may be covered by normal wind erosion. Only the peeling parts of the paint need to be repaired for paint repairs. Dirt, paraffin, and other grime will need to be removed with alcohol from the parts to be repaired prior to paint repairs. Touch-up paint is not recommended for repairing large areas, as touch-up paint does not air dry as well as factory pre-painted. Consult the building panel manufacturer or coating supplier for a suitable gunning system. Aerosol or spray repairs are not recommended for scratch defects. A better repair tool is a high-quality, 1/2-inch or smaller paint brush. If maintained as described above, color coated boards will retain their original color for a long time.

Hungthai Metal is a professional steel manufacturer and exporter. Color coated steel coil is also called prepainted galvanized steel coil, PPGI, PPGL in China, as a PPGI and PPGL manufacturer and exporter in China, we use our own high-quality galvanized steel coil and galvalume steel coil to produce color coated steel coil.

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Main uses and industries of galvanized sheet

The use of galvanized sheet industry has been very common, and many galvanized sheets are used in the automotive industry, refrigerated vehicles, construction industry, natural ventilation and heating equipment and furniture manufacturing and other industries, mainly including the following engineering construction, household appliances, furniture, transportation , steel products and other daily necessities and other industries.

Galvanized sheet is used in the construction industry: roofs, roof prefabricated components, living balcony control panels, balconies, newsstands, warehouses, electric rolling shutters, electric heaters, precipitation pipes, etc.

Galvanized sheet is used in electrical products: refrigerators, automatic washing machines, high-voltage switch cabinets, air conditioners, microwave ovens, bread machines, printers, vending machines, fans, vacuum cleaners, etc.

Galvanized sheet is used in the home improvement industry: lamp covers, wardrobes, dining tables, bookcases, bank counters, billboards, medical equipment, etc.

Galvanized sheets are used in the transportation manufacturing industry: trolley ceilings, car chassis, car box panels, large tractors, electric vehicles, shipping containers, highway courtyard walls, freighter compartment panels, etc.

Galvanized sheet is used in other aspects: traditional musical instrument casings, trash cans, billboards, clocks, photographic equipment, meters, etc.

Galvanized sheet is used in other steel product manufacturing industries: color-coated thick steel sheet should be based on hot-dip galvanized sheet, hot-dip galvanized sheet, electro-galvanized sheet, etc., after surface preparation Strips, electro-galvanized strips, electroplated tin plates, and galvanized plates are restrained and formed, and include connecting hooks, which can firmly connect the steel mesh and the pole without all spare parts. Galvanizing has become a key anti-corrosion method for steel, not only because zinc can produce a high-density protective layer thickness on the steel surface, but also because zinc has the actual effect of pipeline cathodic protection. to avoid corrosion of iron butt welds.

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