Roll forming is the most commonly used method for the production of building roofing panels and wall panels with color coated boards. Roll forming machines use a series of differently shaped rolls on a rack to press the steel rolls into the required shape.

Color-coated steel sheet is pressed into various shapes according to the strength and elongation of the steel sheet, coating characteristics, the model of the forming machine and the maintenance status.

Color coated galvanized steel coil

In order to improve the on-site performance of the color plate, especially the deformation area of ​​the steel plate, the following requirements should be observed:

(1) Adopting a large bending center radius design can meet the deep shape requirements of architectural design.

(2) Roll design meets the deformation of the steel plate from the middle to the side.

(3) The rolling design is matched with the strength of the steel plate. For example, for high-strength steel plates, the deformation of the same shape may require more deformation passes.

(4) Low-strength steel plates should be selected for complex shapes to allow greater design margin.

(5) Maintain the rolling equipment so that it has the required horizontality and verticality, and sufficient rotating roller clearance to avoid scratching the coating and cleaning the rollers to avoid damage to the topcoat.

Color steel plate

(6) The flexible primer and topcoat system are used to increase the performance of the steel plate during bending.

Although roll forming is the most commonly used method for color-coated sheet forming, for the production of roof panels and wall panels, blanking or other accessories may be required. For the same reason, the largest bend radius is needed to improve the performance of the bending part.

It is also very important to avoid scratches on the surface of the coating during the blanking process. Measures to protect the coating surface from scratches can be taken with a stamper protective film. Proper mold clearance should be maintained during pressing.

Embossing is a type of color-coated sheet molding. The embossing process needs to ensure that the plating and coating are not damaged. It needs a sufficiently low embossing sharpness and depth to ensure that the durability of the color-coated sheet is not affected.

Other forming methods for color coated plates include stamping, slotting and perforating. Many of the influencing factors discussed previously, such as die clearance and coating flexibility, are as important as the above forming methods.

Hot-dip galvanizing, also called hot-dip galvanizing, is a method of obtaining a metallic coating by immersing steel components in molten zinc. With the rapid development of high-voltage power transmission, transportation, and communications in recent years, the requirements for protection of iron and steel parts have become higher and higher, and the demand for hot-dip galvanizing has also increased.

Protective properties of hot-dip galvanized layer

Usually the thickness of the galvanized layer is 5-15um, while the hot-dip galvanized layer is generally above 65um, even as high as 100um. Hot-dip galvanizing has good covering ability, dense plating and no organic inclusions. As we all know, the mechanism of zinc’s resistance to atmospheric corrosion includes mechanical protection and electrochemical protection. Under the condition of atmospheric corrosion, there are protective films of Zn0, Zn (OH) 2 and basic zinc carbonate on the surface of zinc layer, which can slow down the corrosion of zinc to a certain extent. If the protective film (also called white rust) is damaged, a new layer will be formed.

When the zinc layer is severely damaged and the iron matrix is ​​endangered, zinc generates electrochemical protection for the matrix. The standard potential of zinc is -0.76V, the standard potential of iron is -0.44V. When zinc and iron form a microbattery, zinc is dissolved as an anode, and iron is dissolved. Protected as a cathode. Obviously, the hot-dip galvanizing ability of the base metal iron is better than that of electro-galvanizing.

Formation process of hot-dip galvanized layer

The process of hot-dip galvanizing layer formation is the process of forming an iron-zinc alloy between the iron substrate and the outermost pure zinc layer. The surface of the workpiece is formed with an iron-zinc alloy layer during hot dip plating, which makes the iron and pure zinc layer very Good combination, the process can be simply described as follows: when an iron workpiece is immersed in molten zinc liquid, zinc and a iron (body-centered) solid solution are first formed on the interface. This is a crystal formed by dissolving zinc atoms in the solid state of the base metal iron. The two metal atoms are fused and the attraction between the atoms is relatively small.

Therefore, when zinc reaches saturation in the solid solution, the two elements of zinc and iron diffuse into each other, and the zinc atoms diffused into (or infiltrated into) the iron matrix migrate in the matrix of the matrix, gradually form an alloy with iron, and diffuse The iron in the molten zinc solution forms an intermetallic compound FeZn13 with zinc, which sinks into the bottom of the hot-dip galvanizing pot, which is zinc slag. When the workpiece is removed from the zinc bath, a pure zinc layer is formed on the surface, which is a hexagonal crystal with an iron content of not more than 0.003%.


Crafting process

Workpiece degreasing → water washing → pickling → water washing → dip assisting plating solvent → drying and preheating → hot galvanizing → finishing → cooling → passivation → rinsing → drying → inspection

Process description

(1) Skim

Chemical degreasing or water-based metal degreasing cleaning agents can be used to remove the oil until the workpiece is completely wetted with water.

(2) Pickling

It can be pickled with H2S0415%, thiourea 0.1%, 40 ~ 60 ℃ or HC120%, hexamethylenetetramine 1 ~ 3g / L, 20 ~ 40 ℃. Adding a corrosion inhibitor can prevent over-corrosion of the substrate and reduce the hydrogen absorption of the iron substrate. Poor degreasing and pickling treatment will cause poor adhesion of the coating, and zinc will not be plated or the zinc layer will fall off.

(3) Dip plating agent

Also called bonding agent, it can keep the workpiece active before immersion plating to enhance the bonding between the coating and the substrate.

NH4C115% ~ 25%, ZnC122.5% ~ 3.5%, 55 ~ 65 ℃, 5 ~ 10min. In order to reduce the volatilization of NH4C1, glycerin can be added appropriately.

(4) Drying and preheating

In order to prevent the workpiece from being deformed due to the sharp rise in temperature during immersion plating, and to remove the residual moisture, to prevent the occurrence of zinc explosion, which will cause the zinc liquid to splash, the preheating is generally 120 ~ 180 ° C.

(5) Hot-dip galvanizing

It is necessary to control the temperature of the zinc solution, the immersion time and the speed of removing the workpiece from the zinc solution. Too low temperature, poor liquidity of zinc liquid, thick and uneven coating, easy to produce sagging, poor appearance quality; high temperature, good liquidity of zinc liquid, zinc liquid easily detached from the workpiece, reducing the occurrence of sagging and wrinkling, adhesion Strong, thin coating, good appearance, and high production efficiency; but the temperature is too high, the workpiece and zinc pot iron damage is serious, a large amount of zinc slag is generated, which affects the quality of the zinc immersion layer, the zinc consumption is large, and even can not be applied.

At the same temperature, the immersion plating time is long and the plating layer is thick. When the same thickness is required at different temperatures, high temperature dip plating takes longer.

In order to prevent high-temperature deformation of workpieces and reduce zinc slag due to iron loss, general manufacturers use 450 ~ 470 ℃, 0.5 ~ 1.5min. Some factories use higher temperatures for large workpieces and cast iron, but avoid the temperature range of the peak iron loss. In order to improve the fluidity of the hot-dip plating solution at a lower temperature, prevent the coating from being too thick, and improve the appearance of the coating, 0.01% to 0.02% of pure aluminum is often added. Aluminum should be added in small quantities.

(6) Finishing

The finishing of the workpiece after plating is mainly to remove the residual zinc and zinc knobs on the surface, either by vibration or manual methods.

(7) Passivation

The purpose is to improve the surface corrosion resistance of the workpiece surface, reduce or prolong the appearance of white rust, and maintain the good appearance of the coating. All are passivated with chromate, such as Na2Cr20780 ~ 100g / L, sulfuric acid 3 ~ 4ml / L.

(8) Cooling

It is generally water-cooled, but the temperature should not be too low to prevent the workpiece, especially the casting, from cracking in the matrix structure due to chilling and shrinking.

(9) Inspection

The appearance of the coating is bright, detailed, and free from sagging and wrinkling. Coating thickness gauge can be used for thickness inspection. The method is relatively simple, and the thickness of the coating can also be obtained through conversion of zinc adhesion. The bonding strength can be bent with a bending press, and the sample is bent at 90 ~ 180 °. There should be no cracks and coatings falling off, and it can also be tested by hammering.

Control of zinc ash and zinc slag


(1) Formation of zinc ash and zinc slag

Zinc ash and zinc slag not only seriously affect the quality of the zinc coating, cause the coating to be rough, and produce zinc knobs. Moreover, the cost of hot-dip galvanizing is greatly increased. Normally, the workpiece consumes 80 ~ 120kg zinc per 1t of plating. If the zinc ash and zinc slag are serious, its zinc consumption will reach 140 ~ 200kg. Zinc-carbon control is mainly to control the temperature and reduce the dross produced by the surface oxidation of the zinc solution.

Some manufacturers in China are covered with refractory sand and charcoal. Foreign countries use ceramics or glass balls with small thermal conductivity, high melting point, small specific gravity, and no reaction with zinc liquid, which can reduce heat loss and prevent oxidation. Such balls are easily pushed away by the workpiece and are non-sticky to the workpiece Attached effect.

For the formation of zinc slag in the zinc solution, the zinc-iron alloy with extremely poor fluidity is formed when the iron content dissolved in the zinc solution exceeds the solubility at this temperature. The key to high zinc costs.

From the solubility curve of iron in zinc solution, it can be seen that the amount of dissolved iron, ie, the amount of iron loss, is different at different temperatures and different holding times. When the temperature is around 500 ° C, the iron loss increases sharply with the heating and holding time, and it is almost linear. Below or above the range of 480 ~ 510 ℃, iron loss increases slowly with time. Therefore, people call 480 ~ 510 ℃ the malignant dissolution zone. In this temperature range, the zinc solution has the most severe corrosion on the workpiece and the zinc pot. The iron loss has increased significantly above 560 ° C. Above 660 ° C, zinc is a destructive attack on the iron substrate. . Therefore, plating is currently performed in two regions of 450 to 480 ° C and 520 to 560 ° C.

(2) Control of the amount of zinc slag

To reduce zinc slag, we must reduce the iron content in the zinc solution, which is to start from the factors that reduce the dissolution of iron:

a. As far as possible, the material of zinc pot should be welded with carbon steel and low silicon content. The high carbon content will accelerate the corrosion of the iron pot by the zinc liquid, and the high silicon content can also promote the corrosion of the zinc liquid to the iron. At present, 08F high-quality carbon steel plates are mostly used. It contains 0.087% carbon (0.05% ~ 0.11%), silicon ≤ 0.03%, and contains elements such as nickel and chromium that can inhibit iron from being etched.

Do not use ordinary carbon steel, otherwise the zinc consumption is large and the life of the zinc pot is short. It has also been proposed to use silicon carbide to make a molten zinc bath. Although the iron loss can be solved, the modeling process is also a problem.

b. Always slag. First raise the temperature to the upper limit of the process temperature so that the zinc slag is separated from the zinc liquid, and then drop below the process temperature. After the zinc slag sinks to the bottom of the tank, it is fished with a spoon. Plating parts that have fallen into the zinc solution must be salvaged in time.

c. To prevent the iron in the flux from being brought into the zinc bath with the workpiece, the red-brown iron-containing compound will be generated after the flux is used for a certain period of time, and it should be filtered off regularly. It is better to maintain the pH of the flux at about 5.

d. Less than 0.01% of aluminum in the plating solution will accelerate the formation of slag. Appropriate amount of aluminum will not only improve the fluidity of the zinc solution, increase the brightness of the coating, but also help reduce zinc slag and zinc ash. A small amount of aluminum floating in the liquid is beneficial to reduce oxidation, too much affects the quality of the coating, and produces defects.

e. Heating and heating should be uniform to prevent explosion and local overheating.

Color steel plates are often used in construction projects. It is indispensable today, but it is worth mentioning that there are many types of color steel plates and their thicknesses have individual differences. Many people do not understand the specific specifications. , How to choose the thickness of the color steel plate is even more difficult to start, then how to choose the thickness of the color steel plate?

Generally speaking, the color steel plate is divided into two layers, and the size depends on the customer’s requirements. In most cases, 0.476MM color steel plate is used for the lower layer, 950-type tongue and groove board is used for the wall surface, and 0.376 color steel plate is used for the inside and outside. Of course, there are special circumstances, and some mobile homes are galvanized steel with a thickness of 0.35–0.4 mm.

If it is an outdoor simple color steel plate movable room, the color steel plate wall plate uses a 0.4 cm thick galvanized plate, the zinc content of the galvanized is 60-80 grams, and the foam material for the sandwich filler can be used.

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Standard information on the thickness of color steel plates used in international standard purification plants, operating rooms, etc. Wall mobile rooms should use a thickness of 0.6 cm or more, and the zinc content of galvanized should be over 110 grams. The purpose is to prevent rust and fill the color steel plates. It is forbidden to use polyvinyl chloride, that is, foam board, and the fire rating has national standards.

The outer layer of the wall is made of G550 high strength color aluminized zinc steel plate, and the thickness of the substrate is not less than 0.60mm. The inner layer is made of high-strength aluminum-zinc plated steel, and the thickness of the substrate is not less than 0.50mm. The thickness error is ± 0.02mm. The wall insulation material is ultra-fine glass wool.

Color steel plate coating weight: the amount of aluminized zinc ≥180g / m2 (front and back);

Wall panel: AZ185 hot-dip aluminized zinc steel plate;

Paint coating: 20um thick fluorocarbon topcoat on the front of the outer panel, 5um thick epoxy primer;

Organic coating: PVDF fluorocarbon-polyester coating system is selected;

15um thick polyester finish on the front of the inner panel, 5um thick epoxy primer;

20um thick polyester topcoat on the back, 5um thick epoxy primer;

Color steel plate thickness (substrate): outer plate ≥0.6;

5um thick polyester finish on the back, 5um thick epoxy primer.

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The polystyrene color steel sandwich panel is composed of two layers of color-coated steel sheets inside and outside, and is coated with adhesive glue on the steel sheet by an automatic composite molding machine, and thin-wall channel steel is embedded on both sides of the sheet. And blanks made of sheet.

Machine plate specifications: L × 1150 × 50mm, L × 1150 × 75mm, L × 1150 × 100mm, color steel plate manual plate specifications: L × 985 × 50 color steel plate thickness: 0.426mm, 0.476mm, 0.50mm, 0.60mm , Polystyrene density ≥18kg / m3 Thermal conductivity: 0.041w / mk Combustion performance: B1 level (flammability), the maximum operating temperature is 100.

In the production process of color steel plate, the thickness dimension must be carried out according to certain specifications. Among them, the thickness of the color steel plate is required to be between 50-250mm. If it exceeds the specified range, it is regarded as a substandard product.

The requirements for the size of the color steel plate are: the width is generally 1150mm, and the length can be changed according to user needs. The thickness and size of the color steel plate largely determines the role and function of the color steel plate, so it is necessary to strictly control the production process.

Color-coated sheet is made of cold-rolled steel sheet and galvanized steel sheet as the substrate. After surface pretreatment (degreasing, cleaning, chemical conversion treatment), coating is applied in a continuous method (roller coating method), and baked and cooled The product.

The color-coated steel plate refers to the color-coated steel plate, and the color-coated steel plate is a steel plate with an organic coating. Color steel plate is divided into veneer, color steel composite plate, floor bearing plate and so on. So what is the difference between the two, the color steel plate manufacturers will tell you what are the specific differences between them.

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The specific differences are as follows:

1. During the refining process, the substrate of the color-coated board is a steel strip used for coating. The front and back of the color-coated board are very important. Usually, the two surfaces of the color-coated board have color, coating properties, and High quality requirements. Color-coated board has strong hardness and flexibility. Its coating is resistant to mechanical effects such as scratches, friction, collision, and press-in. The coating of the color-coated board and the substrate are deformed together without damage. .

From the end of production, color-coated boards have an interval between the performance of the original coating and the time it must be overhauled to maintain its protective effect on the substrate. Under the influence of use and over time, it will gradually deteriorate, and a major repair must be performed to make it more durable.

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2. The color steel plate is based on cold-rolled steel plate, and after degreasing and phosphating, it is hot-dip galvanized on both sides under the protection of nitrogen, and a chemical conversion film that is easy to adhere firmly to the primer is applied. He was painted with an epoxy primer, and finally a chemical-resistant color finish.

The color plate is a color steel plate, which is coated with a layer of polymer material on the steel plate, which is divided into one side and two sides. Most of the single side has a pattern on the surface.

The above two major points are the differences between the color coated plate and the color steel plate. Although the two names are similar, the production method and the scope of application are different, so we must choose our own according to our actual situation when choosing to use it. We need to learn to distinguish between the required product and the type of building used in different boards. Only boards that meet the requirements for use can play a good effect.

Galvanized steel refers to a steel plate whose surface is coated with zinc. Galvanizing is a frequently used economical and effective anticorrosive method, and about half of the world’s zinc production is used for this process. Hot-dip galvanized steel has the advantages of ideal comprehensive properties such as corrosion resistance, forming and coating, as well as low cost and good appearance.

Galvanized steel application

Galvanized steel is mainly used in construction, light industry, automotive, agriculture, animal husbandry, fishery and commercial industries.

The construction industry is mainly used to manufacture anti-corrosive industrial supplies and panels, roof grids, balcony panels, windowsills, newsstands, warehouses, rolling doors, heaters, rainwater pipes, etc. used in civil construction houses;

The light industry uses it to make housings for household appliances, civilian chimneys, kitchen utensils, etc. The automotive industry is mainly used to make corrosion-resistant parts for cars, etc .;

Galvanized steel coil for roofing panels

Agriculture, animal husbandry and fishery are mainly used for grain storage and transportation, frozen processing of meat and aquatic products, etc .;

Commerce is mainly used for storage and transportation of materials, packaging appliances, etc. Household appliances such as refrigerators, washing machines, switch cabinets, air conditioners, microwave ovens, toasters, copiers, vending machines, fans, vacuum cleaners, etc. will also use galvanized sheet.

Hot dip galvanized steel shee

Classification of galvanized steel

Galvanized sheet is divided according to the layout: there are zinc flower galvanized sheet and non-zinc flower galvanized sheet.

According to zinc layer thickness: 80G zinc; 100G zinc; 120G zinc; 180G zinc; 275G zinc.

According to production and processing methods can be divided into the following categories:

(1) Hot-dip galvanized steel sheet. The steel sheet is immersed in a molten zinc bath, and a layer of zinc steel sheet is adhered to the surface. At present, it is mainly produced by continuous galvanizing process, that is, the coiled steel sheet is continuously immersed in a zinc plating bath with molten zinc to make a galvanized steel sheet;

(2) Galvanized steel sheet. This steel sheet is also manufactured by the hot-dip method, but immediately after it is out of the tank, it is heated to about 500 ° C to form an alloy thin film of zinc and iron. This galvanized sheet has good paint adhesion and weldability;

Galvanized steel coil for roofing panels

(3) Galvanized steel sheet. The galvanized steel sheet produced by electroplating has good workability. But the coating is thin, and the corrosion resistance is not as good as the hot-dip galvanized sheet;

(4) Single-side and double-side differential galvanized steel. Single-sided galvanized steel, that is, products with only one side galvanized. In welding, painting, anti-rust treatment and processing, it has better adaptability than double-sided galvanized sheet. In order to overcome the shortcomings of uncoated zinc on one side, there is another type of galvanized sheet coated with a thin layer of zinc on the other side, that is, a double-sided galvanized sheet;

(5) Alloy and composite galvanized steel sheet. It is made of zinc and other metals such as aluminum, lead, zinc, etc. and even composite plated steel plates. This steel sheet has both excellent anti-rust performance and good coating performance.

In addition to the above five types, there are color galvanized steel sheets, printed coated galvanized steel sheets, and polyvinyl chloride laminated galvanized steel sheets. However, the hot-dip galvanized sheet is still the most commonly used.

The main component of color-coated steel coating is resin, which is the base material in the coating formulation. In addition, most coatings require solvents and can also contain various additives. In addition, many coatings also contain a cross-linking agent. After the coating is applied to the substrate, it chemically reacts with the resin during the curing stage to form a network-like cross-linked paint film. This network structure is very necessary to produce good paint film performance. After the coil coating is applied at high speed, it will cure quickly under high temperature (15-30 seconds). The solvent must evaporate during the curing stage to form a coating film.

Many properties are important for the coating film, including hardness, flexibility, weather resistance, chemical resistance, solvent resistance, corrosion resistance, adhesion to various substrates, impact resistance, and so on. These properties depend on many factors, including the type, molecular weight, monomer composition, and glass transition temperature (Tg) of the resin; the type and amount of crosslinking agent; curing conditions; curing catalyst; and auxiliaries. Changing these parameters can result in large changes in paint film properties to meet the requirements of many different applications.

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Color coated steel coating types

According to different coatings, coatings can be divided into three categories: primer, topcoat and backcoat:


The primer is divided into polyester primer, polyurethane primer, epoxy primer, etc. according to the film-forming resin. Different primers can be selected according to the needs of the user. Commonly used are epoxy primers and polyurethane primers, which are manufactured with anti-rust pigments such as zinc chrome yellow and silver yellow.


Generally use polyester resin, high weather resistance polyester resin, silicon modified polyester resin, acrylic resin, polyvinylidene fluoride resin, polyurethane, heat curing cross-linking curing system using methyl etherified amino resin or closed isochlorate Resin, and choose high temperature and weather resistance pigment.

Back paint

At present, it can be divided into 2/1, 2/2, and 2 / 1M systems in China. The back of the 2/1 system can be coated with a layer of primer or only a layer of back paint. It is mainly used for sandwich panels, and the coating must have good adhesion and foaming properties. The 2/2 system uses a two-coat system of a primer and a back paint. Generally, foaming performance is not required, and it is used as a veneer. 2 / 1M system, generally coated with 3 micron primer and 6 micron back paint, can replace 2/1, and requires foaming on the back.

Color coated galvanized steel coilCorrosion resistance mechanism of color coated steel plate

In fact, the so-called anti-corrosion mechanism of color-coated steel sheet depends more on the coating type of color-coated steel sheet. At present, the coatings with better corrosion resistance on the market are mainly PVDF fluorocarbon coatings, HDP high weather-resistant polyester coatings, SMP Silicone modified polyester, etc.

PVDF fluorocarbon coating

PVDF fluorinated resin coating (≥70%) began in the 1960s. After more than 60 years of practical use, it has been proven to have excellent weather resistance. It is currently the most excellent weather resistance in coil coatings. It also has extremely high chemical stability.

PVDF resin has excellent UV resistance, but it can’t block UV by itself. The pigment in the coating must be used to block UV and protect the primer from UV. Therefore, the pigment used must have excellent weather resistance and resistance Chemical, able to withstand outdoor exposure for 20-30 years.

Most organic pigments will be degraded or discolored under the action of sunlight and the atmosphere. The chemical properties of inorganic high temperature burned metal oxide pigments are relatively stable and suitable for long-term protection.

In recent years, fluoro resins copolymerized with trifluorochloroethylene and vinyl ester monomers have been widely used in building exterior walls and metal panels. Due to the use of easily hydrolyzed vinyl ester monomers and fluorine, the content is lower than PVDF. Compared with PVDF, its weatherability has a certain gap.

corrugated metal roofing sheetsHDP high weather resistance polyester coating

At present, the color plates used in construction mainly use ordinary polyester coatings. After 8-10 years of use, the coatings will gradually lose light, lose protection and decoration. High weather-resistant polyester (HDP) resins are synthesized using monomers containing cyclohexane structure to achieve a balance of flexibility, weather resistance and cost of the resin, and aromatic-free polyols and polyacids are used to reduce the resin’s exposure to UV. Absorption of light to achieve high weatherability of coatings. Add UV absorber and hindered glue (HALS) to the coating formulation to improve the weatherability of the film.

SMP silicone modified polyester

Conventional silicone-modified polyester coil coatings are modified by cold-working with silicone resin and polyester resin to ensure outdoor weather resistance for 10 years. An effective method is to directly modify the polyester resin with the silicone monomer to further improve the weatherability of the silicone-modified polyester resin, so that the coating can reach the weather resistance of the outdoor for 20 years, and has become a hot spot for development. When modifying polyester resins, methoxy organic silicone intermediates are usually used. When the silicone content reaches 30% of the resin ratio and high-temperature calcined metal oxide pigments are used, the coating can reach 25 years of weather resistance. The performance requirements are second only to fluororesin coatings.

Color-coated steel plates used in construction are mainly affected by ultraviolet rays in sunlight, moisture in the air, and harmful substances caused by industrial pollution to reduce the service life. The anticorrosion of color-coated products for construction is a combination of coatings, pretreatment films and coatings (primer, topcoat and backcoat). This combination is very important and directly affects its service life. In order to improve the field performance of the color plate, especially the deformation area of ​​the steel plate, the regulations in the use guide should be observed.

Corrosion resistance mechanismThe failure process of color-coated steel plates, that is, coating failure, coating failure and even perforation of steel plates are the key corrosion occurrence processes. Therefore, the thickness of the coating layer is increased, and the weather-resistant and corrosion-resistant coating layer is the most effective method to prevent the corrosion failure of the color-coated steel plate.

Coating loss of light → Coating discoloration → Coating differentiation → Coating cracking → Coating blistering → White / red rust at the scratch → Peeling of the incision → Large area of ​​the coating peeling off → Large area of ​​white embroidery on the coating and red rust locally Corrosion and perforation of steel sheet → steel sheet failure

Color steel plates have been widely used in many fields such as industry, civil, home appliances, and machinery since the mid-to-late 1980s. Gradually replaced a variety of carbon, chemical fiber and other materials. At the same time, the color steel plate also encountered many, many problems during use. For example: what kind of board is used in what environment, what brand of board is used, the main and most often encountered problem is how many years can I buy the board!

The color steel plate is from the date of manufacture until the used building or product is dismantled, ending the use of the color steel plate. Some color breeze boards have been used for only a few months, and have been used for several years, decades, or even longer. But what causes the uneven usage time of the color steel plate? The reasons are positive and diverse. Below we make an analysis of several important factors that affect the use time of color steel plates.

First, the choice of color steel coil brand

Before the color steel plate was formed, it was also called color coated coil, color steel coil, color coated plate, color steel plate and other names. The quality and material of color steel coils produced by each factory (brand) are different, which is also the primary factor that affects the use time of color steel plates. The brand of color steel coil is first divided into two categories, large steel mills and small steel mills. In domestic large steel plants, Shanghai Baosteel, Baosteel Yellowstone, Taiwan Huihui (Huihui China), BHP BlueScope, United Iron & Steel, Maanshan Iron and Steel and other domestic first-class steel mills. The sales prices of color coated coils in large steel mills are generally higher than ordinary steel mills. It is for this reason that large steel mills have sufficient costs to improve the quality of color steel coils and make them better. Let color plates last longer.

Color steel plates have been used for more than 10 years. But it really has to reach the useful life of 10 years. It still depends on the material and quality. In order to achieve a service life of more than 10 years, first, the base plate of the color steel plate must reach a certain weight (80-100 grams of galvanized, 70-100 grams of aluminized zinc), and secondly, the oil film thickness must reach 18um -25um, reverse 8-15um. To achieve the above two materials, only large steel mills can do it. Small steel mills can’t do it. Even if they can do it, his price is not low. In this way, the sales advantage of small steel mills is lost.

Second, the material of color steel coil

If you want to use your color steel plate for a long time, choose a big brand, and then choose a good material. As mentioned above, only large steel mills can make high-quality and high-quality color coated rolls. And how do we choose the best among the high-quality materials? Nothing more than two, substrate and topcoat. Domestic large steel mills generally have zinc coatings on the substrate. Double-sided galvanization is 100 g / square, galvanized 120 g / square, galvanized 140 g / square, galvanized 180 g / square, and galvanized 280 g / square. If you want to use it better, use a color steel coil with aluminized zinc substrate. Large steel plants with aluminized zinc coating have 70g / m2 galvanized zinc, 100g / m2 galvanized zinc, 150g / m2 galvanized zinc, 165g / m2 galvanized zinc, 180g / m2 galvanized zinc , Galvanized 200 g / sq., Up to 220 g / sq.

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What needs to be explained here is that the use time of 70 grams of aluminized zinc at some times even exceeds the use time of 140 grams / square galvanized.

Secondly, there is the problem of the topcoat of the color-coated board. The topcoat of the color-coated board is divided into the type of topcoat, the thickness of the topcoat, and the baking time. The types of topcoat can be divided into: ordinary PE polyester topcoat (for general use), PVDF fluorocarbon resin topcoat (for chemical use), SMP polyester topcoat (for temperature and abrasion resistance), HDP high weathering resin surface Paint (for external use in marine climate environment), HPC self-cleaning top coat (for dust pollution), antibacterial polyester top coat (for medical clean environment).

In addition to the type of topcoat, it is the thickness of the topcoat. Regardless of the type of topcoat, in order to meet the quality requirements, a certain thickness of the film must be achieved. For large steel plants, the front paint is generally 18-25um, and the reverse paint is generally 8 -15um. Just like people wear clothes, only when the thickness of the top coat is made enough can it fully resist the erosion of the external environment. Once again, it is the baking time. When the type of topcoat is good and the film thickness of the topcoat is reached, if the baking time is not enough, the topcoat will be easily powdered and peeled off. Ovens in large steel plants are generally 50-200 meters longer than small plants.

Third, molding methods and equipment

Many customers send the colored steel coils to the processing plant, and the paint will fall off as soon as the press is formed, or the paint surface will be surrounded by flowers. This is usually the wrong pressing method, or the baking time of the steel coil is not enough. On the equipment, some equipment is poor, and there are a lot of burrs on the roller.

Fourth, installation method

In many projects, when the color steel plate is installed, workers accidentally scratch the top paint with sharp tools, or when the steel plate is cut with different sizes, red hot cutting iron filings fall on the top paint, causing the top paint to burn. damage. The finish of the color steel plate itself is a whole. If local scratches or burns occur, red rust, perforations will appear on the surface, and finally a large area of ​​rust will leak. There is also an unavoidable rivet. The rivet will definitely penetrate the steel plate, so that the colored steel plate will show the cut surface, and the rain will flow to form rust.

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Fifth, maintenance methods

There are many projects that use good color plates from Dagang, but after the production is completed, they are never managed and maintained. Of course, this is one of the reasons that affects the service life. After installation of the color steel plate, regular cleaning and maintenance are required. Derusting and lacquering should be carried out where rust spots appear locally. The powdering and lacquering treatment is performed on the partially powdered area. Cover in exposed areas.

Sixth, the use environment

The use of color steel plates with different material properties under the previous question in different environments can better extend the use time of color steel plates. Outside the ordinary environment, generally use ordinary PE polyester coated board in color coated rolls. For different environments, different types of color steel coils can be used for more effective prevention and thus reach a certain useful life. The environments that affect the service life of color steel plates generally include the following.

1. Applicable environment. The so-called applicable environment is what your factory will do after it is completed. For example, some factories are used to stack or produce chemical products after the completion of construction. The general color steel plate is definitely not acceptable. It is necessary to use PVDF fluorocarbon color coated plate and the substrate must be more than 150 grams of aluminum zinc plating. Extend the corresponding use time.

2. Climate environment (region). For the climate environment, it is okay for inland areas and flat ones. If you encounter elephants, some are coastal areas (large air humidity), and some are north of the equator (such as Xinjiang is dry all year round). Some are remote mountainous areas (high fog). If the color steel plate is used all year round in such a harsh climate, and the material is not used properly, the color steel plate will soon crack, powder, and peel off. It is recommended to use high weather-resistant color steel plate for such unstable and harsh regions.

3. The industrial environment, the so-called industrial environment, is the surrounding environment other than your own environment. If your plant is used for general stacking or production, there is no other chemical or corrosive things, but there are many heavy industries around you, like chemical plants, or steel or oil refineries, then they will affect the entire area Emission of pollutants, a lot of malignant particle pollution will fly to your plant, causing acid rain for a long time. If your plant is in such a heavy industry polluted area, then you have to consider your plant The selection of materials.

Seventh, storage time and method

Some customers have not used the color steel coils after they bought them back. It took two or three years or even more time to open them for use, and they found that the whole piece of paint cracked or cracked after a press. This situation can only indicate that your storage time is too long, or your storage method is incorrect.

The color steel plate is not afraid of being covered on the roof or wall by wind and rain all the year round, but the whole volume is parked there and wrapped. Because the color steel plate is baked, as soon as it is not ventilated, the painted surface will be damp or sweaty. After a long time, the paint will fall off. The correct storage method for color steel plates is that they should be stored in an indoor warehouse without water at a high place and underneath with wooden boards. And keep dry and ventilated.

Color-coated steel plate is a composite material formed by coating one or more organic coatings on a metal substrate and baking. It is used in home appliances and the construction industry because of its good corrosion resistance and aesthetics. Since the establishment of the first color coating unit in the late 1980s, after 30 years, the number of products produced has increased from 16 colors in the first four coating categories to more than a dozen involving industries and uses such as construction and home appliances. Coating types. Color coated board coatings often encounter some technical problems in use. This article briefly introduces several common problems.

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Flash paint visual error problem

Color-coated board coating topcoats are divided into two categories: “plain paint” and “flash paint” (flash paint is divided into “metal paint” and “pearl paint”). Unlike plain paint, which produces color through the selective absorption and diffuse reflection of light by pigment particles, metal and pearlescent pigments are layered and arranged in the same orientation in parallel to the paint film. When the light hits the surface of the paint film, part of the light Due to the direct reflection of the aluminum powder, there is almost no absorption. Part of the light is particularly bright and gives a very dazzling feeling. Part of the light is reflected by the aluminum powder multiple times, and the light is dark. Therefore, it gives different visual effects when viewed from different angles.

The light generated by the same incident light source increases with the number of reflections, and the light becomes darker. The effect seen at the viewing angle A and the viewing angle B will vary depending on the light. Therefore, the visual effect of the flash paint will depend on the light incident angle (corresponding to Dawn changes in nature, etc.) and observers’ observation positions vary. Therefore, the color difference of flash paint is more difficult to control, and the user sometimes reflects the phenomenon of visual color difference in use.

In steel paint coating management, on the one hand, the same user contract should be selected as much as possible in the production control of the same user contract, and the same batch of paint is produced at the same time to avoid color differences caused by differences in different paints and processes. A multi-angle color difference meter that is closer to the measurement effect of the human eye is used for color difference comparison. On the other hand, it guides the user to help them avoid the problem of color difference caused by different material installation directions.

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Coating adhesion issues

When color coated board is used as a sandwich board, a problem often faced is poor adhesion or foaming. Because when the coating is used to make sandwich panels, the coating must be effectively combined with the foaming agent to ensure the integrity of the sandwich panel. Generally speaking, the problem of bad adhesion encountered by users is “not sticking”.

Not sticking

The back coating of the color-coated board is poorly bonded. The reasons for this problem are mainly as follows:
(1) Glue reaction time: The length of the glue reaction time during processing will affect the foaming effect, and the foaming effect will not be too ideal if the time is too long or too short.

(2) Coating quality: The type of coating determines the surface activity of the coating after curing, which will affect the foaming effect of the color coated board and the foaming agent. If the coating has less reactive groups, the foaming properties will be affected. It is a poor foaming model for coatings with less reactive groups.

(3) Glue quality: Glue for foaming is generally composed of black glue and white glue. White glue is a polyether polyol with hydroxyl group and black glue is a product with cyanate ester. The two are mixed at a certain ratio to form polyurethane , That is, foam material. The active ingredients in the glue seriously affect the foaming effect of the product. If you add other materials to the white glue to reduce costs or replace the polyether polyol with a lower-priced polyester polyol, it will most likely cause poor foaming.

(4) Others: Foaming process and production environment are also important factors affecting the quality of the finished sandwich panel.

In general, you can choose according to the standard color of the factory, which can reduce the workload in the early stage of production. If special colors are needed, because the paint needs to be prepared in the paint factory first, and the various properties can meet the requirements before production, the production time from order to color plate will be longer. In addition to the major color systems of major factories, the main color system standard of the color steel industry is the German European standard color card (1927). The Chinese translation is: Raul color card (RAL K5, RAL K7, … ).

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Color plate color

1. Red: Crimson, crimson (Baosteel Crimson), high-gloss crimson, red, brick red, rust red, brown red, peach red, suede red, ruby ​​red, fluorocarbon red.

2. Orange yellow: orange, orange, orange (baosteel orange), beige, beige (baosteel beige), milk yellow, ivory yellow, medium yellow, lemon yellow (baosteel lemon yellow), earth yellow, camel yellow (baosteel camel yellow) ), Suede yellow.

3. Green: Cardamom green, bean green, deep bean green, deep bean green (baosteel deep bean green), lotus leaf green, broad leaf green, broad leaf green (baosteel broad leaf green), light green, bright green, deep green, dark green, suede green, HD-6013 fluorocarbon cardamom green 001.

4. Blue: Sea blue, sea blue, light blue, sky blue, sky blue (baosteel sky blue), porcelain blue, porcelain blue (baosteel porcelain blue), deep sky blue (baosteel deep sky blue), moonlight blue, fluorocarbon sea blue.

5. Metals: silver ash, silver ash (baosteel silver ash), fluorocarbon silver, gold pink.

6. Gray: gray, gray, light gray, medium gray, light gray, iron blue gray, camel gray, dark gray, fluorocarbon gray, fluorocarbon gray, fluorocarbon light gray, suede gray.

7. Brown black: carbon black, ink black, brown, black, suede black.

8. White series: white gray, white gray (baosteel white gray), white gray (gorgeous gray), ivory white (baosteel ivory white, milky white, milky white (baosteel milky white), magnolia white, emperor white, high light white, snow white, high light snow white, signal white , Moonlight white, pearly white, fluorocarbon white ash.

9. Back paint system: gray back, bud yellow back, steel white back (baosteel color), sky gray back (double coated polyester back), brown back (double coated polyester back).

The gloss of the coating surface measured with a 60 degree reflection angle, the larger the value, the higher the gloss. Generally, the color-coated board for home appliances has high gloss. The coating used on the building is medium or matt, ranging from 30 to 55. This is because the high-gloss coating is used to reflect the sunlight on the building and is dazzling. Indoors, it is easy to cause visual fatigue under the light at night.

Precautions for color coated steel plate design

Galvanized steel coil for roofing panels

Of course, the quality of the color-coated steel sheet mainly depends on the design of the color-coated steel sheet, but if the processing and installation equipment and methods are improper, it will also cause damage to the appearance and service life of the final product to varying degrees.


The good appearance and excellent performance of the color-coated steel sheet awakened the interest of architectural designers and homeowners in showing the roof. The roof no longer just needs to have design features to meet the functions of sheltering from wind and rain. The roof system made of color-coated panels can add the color of other architectural elements, and can obtain the effects brought by the wide-ranging changes of roof panel spokes and joints.

The slope of the roof of the color-coated board building is steep, with a typical value of 3:12 or even higher, which is good for the rapid drainage of rainwater. Roofs with small slopes are not easy to see. Generally, aluminized zinc light panels are used. For roofs with slopes less than 1/4: 12, it is more economical to use aluminized zinc light panels. Facts have proven that after 20 years of use, they still maintain excellent performance.

Color coated galvanized steel coil

Roof panels are usually placed on a frame instead of directly on the comb. The frame can be made of wood or steel. Paper or similar materials are usually placed between the roof slab and the part. The color-coated roof is designed to directly contact the roof structure. The roof slab is usually flat, and small longitudinal ribs can be used to improve strength and molding. Fasteners or concealed clips secure the steel plate to the frame, and the roof panels are stacked or welded together longitudinally.


Building panel manufacturers can provide color-painted wall panels of different shapes in a wide range, and the appearance and required building effects of wall panels in all areas of the wide front can be completely consistent. The high-quality painted steel plate can ensure the consistent color and appearance of the steel plate throughout the project.

Similarly, because the same materials can be used to minimize the connection and transfer technical problems, the parts that have a key impact on the overall design effect can use the same materials, colors and processing methods for large-area exterior parts.

Buildings (roofing panels and exterior wall panels) themselves have material requirements that can be divided into safety performance (impact resistance, wind pressure and fire resistance), residential performance (water resistance, heat insulation and sound insulation), durability (pollution resistance Properties, weatherability and appearance retention), production processability (economy, easy processing, easy maintenance and repair).

For the ultimate owner of the building, safety and service life are paramount. For the design unit, the service life, bearing capacity and appearance are more important. For forming processors of building walls and roofs, the workability (surface hardness, abrasion resistance, plate shape, and steel plate strength) of color coated steel sheets are the first requirements.

Specification and selection of color coated steel sheet for construction

Color coated galvanized steel coil


For buildings, the bearing weight (wind load, snow load, construction personnel and machinery), the span of the building, the design of the rubber distance, etc. all depend on the strength of the steel plate. In other words, there are corresponding standards at home and abroad. Such as China’s GB / T12754-2006 in the United States ASTM653, ASTM792, Japan’s JISG3302, JISG3321, European EN10215, EN10147 and so on. According to the steel type, it is divided into CQ (common commercial grade), DQ (for general stamping), HSS (high-strength structural steel), and FH (full hard steel).


It is most commonly used now. For example, TDC51 produced by Baosteel has a yield strength of 260-320Mpa and a tensile strength of 350-400Mpa. Compared with structural steel, its yield ratio is slightly higher.


As general color plates for construction are roll-formed or composite sandwiches, the material’s stamping performance is not high. Therefore, DQ grades are mainly used in door rings, pipes and other industries.


High-strength structural steel: According to the European standard HSS, it can be divided into 4-5 steels with different strengths, but because ordinary CQ grade materials can already replace low-strength HSS steels, the more commonly used in the market are yield strengths of 280Mpa and 345Mpa. The two steel types are TS280GD and TS350GD produced by Baosteel.

Compared with ordinary CQ, HSS steel has several advantages:

1) Due to the relatively low yield strength, the steel has good fire resistance and shock resistance.

2) For thicker steel plates, it can manufacture long-span arched plates.

3) For general exterior wall and roof panel type, it can be appropriately thinner than CQ material, which can save material consumption.


Full hard steel: It is a type of steel that improves the yield strength of steel plates by controlling the annealing temperature. According to international standards, the yield strength is ≥550Mpa and the tensile strength is ≥570Mpa. This type of material has high strength and low elongation, and is suitable for the use of shallow-shaped formed steel plates, which greatly saves the use of materials.

Dimensional accuracy and shape

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For color coated rolls, dimensional accuracy includes width accuracy and thickness accuracy.


The delivery precision of steel coils commonly used in countries around the world is a positive tolerance, which is the nominal width of the actual delivery width when ordering. The control of these widths is generally considered during cold rolling of the steel sheet, because the subsequent galvanizing and color coating processes will affect the corrosion resistance of the edges if they are trimmed. However, if the positive tolerance of the steel plate is too large, it will exceed the feeding limit of the forming machine. According to experience, it is more appropriate to control it at 0-5mm.


The meaning of the thickness of the color-coated board varies from factory to factory. Some of the thicknesses marked on the labels of color-coated steel coils are the thickness of the substrate, some are the thickness of the substrate + plating thickness, and some are the thickness of the substrate + plating thickness + coating originality. Baosteel currently uses the thickness of the substrate + the thickness of the coating (excluding color coating). Such a thickness calculation method is suitable for the designer of the building, because the strength of the color coating is low, and design margin and safety are considered Sexual aspects should not be taken into account. For the same reason, Baosteel has always followed the positive tolerances in terms of delivery thickness tolerances. In this way, although the processing area per unit ton of steel is reduced, the safety of the final building is guaranteed. The reduction of the steel sheet must be carried out with an increase in strength.

Plate shape

The shape of the steel plate depends on the shape of the formed steel plate. Generally speaking, the different depth of the profiled plate has different requirements on the shape of the original plate. The shallow shape requires higher unevenness. For the sandwich panel, the shape requirement is higher than that of the profiled steel sheet, especially the uniformity of the performance (internal stress) in the width direction is better, otherwise it will affect the bond strength of the sandwich panel. The more popular flat cores (products that replace glass curtain walls) have extremely high requirements for the unevenness and severity of steel plates.

Selection of coating

Color steel plate

The coating is considered to ensure the durability and corrosion resistance of the building. Different applications can meet their service life by choosing different coatings, coatings and thicknesses.


The color coatings currently used for construction are currently hot-dip galvanized and hot-dip galvanized. For color coating, the application areas of the two substrates are not very different. Under relatively acidic environments, aluminized zinc substrates are a better choice. For use in wet, alkaline environments, the advantages of the notch corrosion resistance of galvanized substrates are realized. For the thickness of the coating, the general requirements for roofing panels and exterior wall panels are hot-dip galvanized ≥180g / m2 (about 26um), aluminized zinc ≥100g / m2 (about 27um), in the use environment is in the heavy industry area or the sea At the time, foreign related associations have minimum galvanizing requirements, such as ECCA specifications and Australian standards requiring galvanized layer weight ≥275g / m2 (about 38um), aluminum zinc plating ≥150g / m (about 40um).


The coating should meet the user’s requirements for color and durability. It is also necessary for the processor to satisfy its processing performance. Therefore, when ordering, you need to specify the type of coating, color and gloss, and coating thickness. The functions and selection methods are described below.

(1) Type of coating

The commonly used topcoats of coil steel coatings are polyester (PE), polyurethane (PU), silicon modified polyester (SMP), fluorocarbon (PVDF), high weathering polyester (HDP), primer and back paint. The varieties are epoxy (EP), polyester (PE), polyurethane (PU) and so on.

(2) Color and gloss

The choice of color is mainly based on the matching with the surrounding environment and the owner’s hobby. However, from the perspective of using technology, the light color has strong heat reflection ability and small contrast after powder coating. If it is properly cleaned and maintained, the service life will be long. Will be more beautiful. As for gloss, in the outdoor use of color-coated boards, matting is the earliest phenomenon, especially for high gloss products, the initial matting will be very fast. When the gloss is reduced to about 20, it will remain for a long time. This phenomenon will appear for several months. Therefore, the color coated boards for outdoor buildings are generally low-light. In addition, products from the same color painting factory should be used in the same building. Because color-coated steel sheets from different manufacturers have different coating powdering speeds after a certain number of years of outdoor use, even if the buildings appear to be the same when completed, a visual effect of different colors will appear after a period of time, which will affect the appearance.

(3) Coating thickness

Microscopically, the coating is a porous structure. Water in the air and corrosive media (chlorine ions, etc.) can penetrate through the weak part of the coating, causing corrosion under the film, which causes the coating to foam and peel. In addition, even with the same coating thickness, the secondary coating is denser than the primary coating. According to relevant reports and results of corrosion tests, the front coating must be more than 20um to effectively prevent the intrusion of corrosive media. PVDF products require thicker coatings. The requirements for the back coating depend on the application. The sandwich panel only requires a layer of adhesive primer, and the formed steel panel is also required to be coated with two layers due to the indoor corrosion environment.