For the selection of prepainted steel coils in different regions, mainly the local wind and snow load and corrosive environment should be considered. In terms of the wind and snow load, mainly the safety factor of the building is considered. Although this is related to the mechanical properties of the prepainted steel coil, it is more related to the profiled steel coil, the thickness and the connection between the plates. It is relatively difficult to quantitatively describe the corrosive environment of a region. There are many factors that affect the corrosion of prepainted steel coils.
(1) Corrosive environments in different regions. Temperature: the coating softens at high temperature, and the corrosive medium is easy to adhere. It is easy to penetrate into the base plate, and the oxygen content of the water will increase at high temperature, and the corrosion rate of the prepainted steel coil will increase at a certain temperature. Humidity: the corrosion of the base plate at the incision and processing damaged area belongs to electrochemical corrosion, and it is not easy to form a corrosion battery (ie an electrochemical circuit) when the humidity is low. Temperature difference between day and night: if the temperature difference is large, it is easy to condense, forming galvanic corrosion conditions on bare metal. In addition, the large temperature difference also leads to frequent hot and cold deformation of the coating, which will accelerate the aging and loose of the coating, and the external corrosive medium will easily penetrate into the base plate.
(2) Sunshine time and sunshine intensity. Sunlight is an electromagnetic wave, which is divided into Y-ray, X-ray, ultraviolet light, visible light, infrared light, microwave and radio wave according to the level of energy and frequency. Waves and radio waves have low energy and do not interact with matter. Infrared is also a low-energy spectrum, and it can only stretch or bend the chemical bonds of substances, not break them. Visible light gives everything a rich color. UV spectrum is a high-frequency radiation, which is more destructive than low-energy spectrum. For example, we know that skin dark spots and skin cancer are caused by the sun's UV rays. It can be seen from the above that the sunshine time and intensity affect the structural stability of coating of the prepainted galvalume steel coil, especially in areas with strong UV rays.
(3) Rainfall capacity and the acidity of rainfall. Rainfall acidity is definitely not good for corrosion resistance. However, rainfall capacity has a dual effect. For wall panels and roof panels with large slopes, rainfall has the effect of cleaning the surface of steel plates and washing away surface corrosion products. However, for low-slope roof panels and parts with poor drainage, heavy rainfall is easy to cause corrosion aggravation.
(4) Wind direction and wind speed. The effect of wind direction and wind speed is similar to that of water, and they often exert influence together. It is a test for the connection parts of materials such as prepainted steel coils, because the wind will cause the connection parts to loosen and rainwater will penetrate into the interior of the building.
(5) Corrosive sediment. For example, chloride ions, sulfur dioxide, etc., have an accelerated effect on the corrosion of prepainted steel coils, etc. These sediments mostly occur in the seaside and areas with serious industrial pollution (such as power plants, smelters, etc.).