November 17, 2022
The selection of color-coated boards mainly refers to the selection of mechanical properties, substrate type (type of coating) and coating weight, front coating performance and reverse coating performance. Use, environmental corrosion, service life, durability, processing method and degree of deformation are important factors that should be considered when selecting materials.
Selection of Mechanical Properties, Substrate Type and Plating
Weight Mechanical properties are mainly selected based on factors such as application, processing method and degree of deformation. For example, the roof panel of a building is usually not load-bearing, and the deformation is not complicated during processing, so TDC51D is usually selected. For parts with a relatively large degree of deformation, materials with good formability such as TDC52D and TDC53D should be selected. For components with heavy requirements, appropriate structural steel should be selected according to the design requirements, such as TS280GD, TS350GD, etc. The commonly used processing methods of color-coated sheets include shearing, bending, rolling, etc., and should be selected according to the characteristics of each processing method when ordering. In addition, since the mechanical properties of the substrate are usually used to replace the mechanical properties of the color-coated plate in actual production, and the color-coating process may lead to changes in the mechanical properties of the substrate, attention should be paid to this. Substrate type (type of coating) and coating weight are mainly selected based on factors such as application, environmental corrosion, service life and durability. Anti-corrosion is one of the main functions of the color-coated sheet. The type of coating and the weight of the coating are the main factors affecting the corrosion resistance of the color-coated sheet. Since the color-coated sheets for construction are usually directly exposed to the atmospheric environment, substrates such as hot-dip galvanized sheets and hot-dip galvanized sheets with good corrosion resistance and thick coating are usually selected. In addition, the corrosion resistance of different types of coatings is also different. For example, in the case of the same coating thickness, the corrosion resistance of hot-dip Al-Zn coating is higher than that of hot-dip galvanized coating. In addition, corrosion resistance generally increases as the coating weight increases, so the corrosion resistance of color-coated panels can be improved by using substrates with high corrosion resistance and/or by increasing the coating weight. It should also be noted that there are differences in the corrosion resistance of the trimmed edges of the steel plates with different coating types. In addition, service life and durability are also important factors that cannot be ignored when selecting materials. If long service life and high durability are required, substrates with good corrosion resistance or heavy coating weight should be selected. Since the coating of aluminized zinc materials contains about 55% aluminum (Al), aluminum is an amphoteric metal that reacts with both acids and bases. After cement and water are mixed into concrete sand, it is highly alkaline. In such an alkaline environment, aluminum (Al) will undergo chemical reaction, which will eventually lead to the dissolution of the coating and the loss of anti-corrosion protection. Therefore, it is not suitable for direct contact with wet cement for the color-coated plate of the aluminum-zinc coated board, including the aluminum-zinc coated substrate.
Choice of front coating properties
The choice of front coating performance mainly refers to the choice of coating type, coating thickness, coating color difference, coating gloss, coating hardness, coating flexibility/adhesion, coating durability and other properties.
Topcoat
Commonly used topcoats are polyester, silicon-modified polyester, high-durability polyester and polyvinylidene fluoride, and there are certain differences in hardness, flexibility/adhesion, and corrosion resistance of different topcoats. Polyester is currently the most widely used coating, with average durability, good hardness and flexibility of the coating, and moderate price. Silicon-modified polyester has improved durability and gloss and color retention, but slightly reduced coating flexibility. High-durability polyester combines the advantages of polyester with improvements in durability and is cost-effective. Polyvinylidene fluoride has excellent durability, good coating flexibility, but relatively low hardness, fewer colors available and expensive. For detailed performance indicators of various topcoats, please refer to relevant materials or consult experts. The topcoat is mainly determined according to factors such as use, environmental corrosion, service life, durability, processing method and degree of deformation.
Primer
Commonly used primers are epoxy, polyester and polyhelium ester, and there are certain differences in adhesion, flexibility and corrosion resistance of different primers. Epoxy has good adhesion to the substrate and high corrosion resistance, but is not as flexible as other primers. Polyester has good adhesion to the substrate and excellent flexibility, but its corrosion resistance is not as good as epoxy. Polyurethane is a primer with relatively good overall performance. For detailed performance indicators of various primers, please refer to relevant materials or consult experts. The primer is usually determined by the manufacturer based on the production process, application, environmental corrosivity, and matching relationship with the topcoat.
coating thickness
The corrosion resistance of color-coated sheets is closely related to the thickness of the coating. Generally, the corrosion resistance increases with the increase of the coating thickness. The appropriate coating thickness should be determined based on environmental corrosivity, service life and durability.
Coating color difference
Color difference may occur in the production and use of color-coated boards. Since color difference is affected by various factors such as production batch, color depth, use time, use environment, and purpose, it is usually negotiated by both the supplier and the buyer when ordering.
coating gloss
The gloss of the coating is mainly selected according to the application and usage habits. For example, domestic color-coated panels for construction usually choose medium and low gloss, and color-coated panels for home appliances usually choose high gloss.
Coating hardness
The hardness of the coating is the ability of the coating to resist scratches, friction, collision, indentation and other mechanical effects, and is closely related to the scratch resistance, wear resistance, indentation resistance and other properties of the color-coated sheet. It is mainly based on the application. , processing methods, storage and transportation conditions, etc.
Coating flexibility/adhesion
The flexibility/adhesion of the coating is closely related to the machinability of the color-coated sheet, and the selection is mainly based on the processing method and the degree of deformation. When the deformation speed is fast and the deformation degree is large, the color-coated plate with high impact energy value and small T-bend value should be selected.
Coating Durability
Coating durability is the performance of the color-coated sheet during use, and it is usually measured by the length of service life. Coating durability is mainly affected by factors such as coating type, coating thickness, and environmental corrosion. The true durability of coatings can be determined by atmospheric exposure testing. Durability can also be assessed by artificial aging tests. Neutral salt spray resistance test is one of the simplest and most commonly used artificial aging test methods, and UV lamp accelerated aging test is also a commonly used artificial aging test. In addition, the color-coated board may be used in special environments such as acid rain and humidity. At this time, the corresponding artificial aging test should be selected for evaluation. It should be noted that artificial aging tests usually cannot fully simulate the actual use environment.
