Coating color selection of pre-painted board
Summary: The choice of color is mainly based on the matching with the surrounding environment and the owner’s hobbies, but from t...
The choice of color is mainly based on the matching with the surrounding environment and the owner’s hobbies, but from the perspective of the use of technology, the choice of pigments for light-colored paints is large, and inorganic paints with superior durability (such as titanium dioxide, etc.) can be selected. The heat reflection ability is strong (the reflection coefficient is twice that of the dark paint). The temperature of the coating itself is relatively low in summer, which is beneficial to the extension of the life of the coating. In addition, even if the coating is discolored or powdered, the contrast of the light-colored coating film with the original color after the change is small, and the effect on the appearance is not large. The dark colors (especially the more vivid colors) mostly use organic colors, which are easy to fade when exposed to ultraviolet light, and change color in the shortest 3 months.
At present, a large number of coatings used in color coating for construction are hot-dip galvanizing and galvanizing. The greater the thickness of the coating, the better the corrosion resistance.
The thickness of the coating mainly affects the notch corrosion performance of the color-coated steel sheet. The notch corrosion is electrochemical corrosion. The influencing factors include the pretreatment layer, primer, substrate thickness, and coating thickness. Under normal circumstances, the pretreatment layer and the primer are relatively fixed, and the thickness of the substrate and the thickness of the plating layer affect the corrosion performance of the cut. The thinner the substrate and the thicker the coating, the better the performance of notch corrosion resistance. Regarding this point, there are many studies in the world, and the more widely recognized zinc ratio is currently. That is, the number of grams of the coating weight per square meter on one side of the coating/the thickness of the substrate (in millimeters). It is believed that a zinc ratio greater than 100 is a guarantee for effectively preventing the cut corrosion of the color-coated steel sheet. For example, if the steel plate is 0.6mm, the galvanizing amount on one side will reach 60g/m2. Although the corrosion resistance of aluminized zinc plate is better than that of hot-dip galvanizing, the zinc ratio is also suitable for hot-dip galvanizing for the spread of cut corrosion.
As for the choice of hot-dip pure zinc or hot-dip aluminum-zinc for the coating, it mainly depends on the pH of the environment in which it is used. Zinc and aluminum are both amphoteric metals, but their performance in acids and alkalis is different. The performance of pure zinc in alkaline medium is better than that of aluminum-zinc alloy. The performance in pickling medium is the opposite. Therefore, it is recommended to use aluminized zinc color coating in a relatively acidic environment, and hot-dip pure zinc color coating in a relatively alkaline environment. According to experience, do not touch the aluminum-zinc-plated substrate for a long time with wet wood and concrete.
In China, for the selection of color-coated steel plates, users are relatively less concerned about steel types. Because most of the domestic color-coated steel production plants have fewer types of steel, most of them are DC51 (because they purchase hot-rolled plates or rolled hard coils, which are basically the same steel type), and some color-coated steel plants with hot-dip galvanizing production lines It is very difficult to produce full-hard steel (S550) or high-strength steel (S350, etc.) through hot-dip galvanizing and annealing, because they cannot control the quality and chemical composition of the substrate. Therefore, the quality stability is poor, which leads to large performance fluctuations and causes deterioration of the profiled board.
For buildings, the load-bearing weight (wind load, snow load, construction personnel and machinery), the span of the building, the design of the purlin, etc. all depend on the strength of the steel plate. For the building maintenance structure, color coating and aluminum-zinc plate are used In other words, there are corresponding standards in foreign countries. Such as ASTM653 and ASTM792 in the United States, JISG3302 in Japan, JISG3321 in Japan, and EN10215 and EN10147 in Europe. According to steel types, it is divided into CQ (common commercial grade), DQ (general stamping), HSS (high-strength structural steel), and FH (full hard steel).