The use environment of color coated steel coils

On the continuous unit, cold-rolled strip steel and galvanized strip steel (electro-galvanized and hot-dip galvanized) are used as the substrate. After surface pretreatment (degreasing and chemical treatment), one or more layers of liquid are applied by roller coating. Coating, the plate obtained after baking and cooling is the coated steel plate. Since the coating can have various colors, it is customary to call coated steel plates color-coated steel plates. And because the coating is carried out before the steel plate is formed and processed, it is called pre-coated steel plate abroad. Process flow:
Color-coated steel plates are made by using cold-rolled steel plates and galvanized steel plates as base plates. They undergo surface pretreatment (degreasing, cleaning, chemical conversion treatment), are coated with paint in a continuous method (roller coating method), and are baked and cooled. finished product. The main production processes of the common two-coating and two-baking continuous color coating unit are: uncoiling - pretreatment + coating - → baking → post-processing → coiling. Environmental factors of corrosion:
Longitude and latitude, temperature, humidity, total radiation (ultraviolet intensity, sunshine hours), rainfall, pH value, wind speed, wind direction, corrosive sediments (C1, SO2).

Effects of sunlight:
Sunlight is an electromagnetic wave, which is divided into gamma rays, X-rays, ultraviolet rays, visible light, infrared rays, microwaves and radio waves according to the energy and frequency. Ultraviolet spectrum (UV) is high-frequency radiation and is more damaging than low-energy spectrum. For example, we know that dark spots on the skin and skin cancer are caused by the sun's ultraviolet rays. UV light can also break the chemical bonds of a substance, causing it to break, depending on the wavelength of the UV light and the strength of the substance's chemical bonds. X-rays are penetrating, and gamma rays can break chemical bonds and produce free charged ions, which are fatal to organic matter.

Effect of temperature and humidity:
For metal coatings, high temperatures and moisture can cause oxidation reactions (corrosion). Color-coated boards have been exposed to high temperatures for a long time, and the molecular structure of the surface paint is easily destroyed. When the humidity is high, condensation is easy to form on the surface and the tendency of electrochemical corrosion is enhanced.

Effect of ph value on corrosion performance:
As for metal deposits (zinc or aluminum), they are both amphoteric metals and can be corroded by strong acids and alkalis. However, different metals have different acid and alkali resistance capabilities. Galvanized sheets have slightly stronger alkali resistance, and aluminum-zinc sheets have slightly stronger acid resistance.

Effects of rain:
The resistance of rainwater to painted panels depends on the structure of the building and the acidity of the rainwater. For buildings with steep slopes (such as walls), rainwater has a self-cleaning function that prevents further corrosion, but if the casting has a smaller slope (such as a roof), rainwater will settle on the surface for a period of time. For a long time, it promotes hydrolysis of the coating and water penetration. For seams or cuts in steel plates, the presence of water increases the possibility of electrochemical corrosion, orientation is also important, and acid rain is more serious.