In ordinary atmospheric environment, although the humidity and pollutant content are relatively low, long-term exposure will still cause oxidation and rust of channel steel frame. For such environment, coating protection is the most basic and effective solution. First, the surface of channel steel frame needs to be pretreated. Through sandblasting, shot blasting and other methods, the rust, oil, dust and other impurities on the surface are thoroughly removed to make the steel surface reach a certain roughness and enhance the adhesion of the coating. Then, a composite coating system consisting of primer, intermediate paint and topcoat is applied. The primer can be epoxy zinc-rich primer, which uses the sacrificial anode protection of zinc to provide electrochemical protection for steel; the intermediate paint increases the coating thickness and improves the anti-corrosion performance; the topcoat plays an anti-ultraviolet, anti-aging and decorative role. For example, polyurethane topcoat can effectively resist water vapor and oxygen erosion in the atmosphere. Generally, the total coating thickness is controlled at 150-200 microns, which can provide 3-5 years of effective protection for channel steel frame.
In high humidity environment, such as coastal areas, southern rainy season or channel steel frame in a humid basement for a long time, moisture can easily form a water film on the surface of the steel, accelerating the electrochemical corrosion process. In view of this situation, in addition to conventional surface treatment and coating processes, further strengthening of protective measures is required. Solvent-free epoxy coating can be used. The coating has a 100% solid content and no pores after film formation, which can effectively block water vapor penetration; at the same time, the coating thickness is increased to 250-300 microns to form a denser protective layer. In addition, corrosion inhibitors can be used in combination. Before coating, the corrosion inhibitors can be applied to the surface of the steel. Its molecules can be adsorbed on the metal surface to form a protective film and slow down the corrosion rate. Through these comprehensive measures, the corrosion resistance of channel steel frames in high humidity environments can be significantly improved and their service life can be extended.
In an environment with severe industrial pollution, such as around chemical plants and metallurgical plants, the air contains a large amount of corrosive media such as acid mist, alkali mist, salt mist and sulfide, which have a strong corrosive effect on channel steel frames. In this environment, the first thing to do is to choose a coating with excellent chemical corrosion resistance, such as vinyl ester resin coating, which has extremely strong acid, alkali and solvent resistance. In the coating process, multi-layer coating is used to increase the shielding effect of the coating. For example, the primer uses epoxy glass flake coating. The layered structure of glass flakes can effectively extend the penetration path of the corrosive medium; the intermediate paint and topcoat use high-performance fluorocarbon coatings, which have excellent weather resistance and chemical stability and can resist the erosion of harsh pollutants. In addition, regular cleaning of the channel steel frame to remove corrosive pollutants attached to the surface is also an important protective measure.
In the marine environment, high salt spray, high humidity and strong ultraviolet radiation make the channel steel frame face severe corrosion challenges. For the marine environment, a combination of heavy anti-corrosion coating system and cathodic protection is required. Heavy anti-corrosion coating generally uses epoxy coal tar paint or epoxy powder coating. The former has good water resistance and salt spray resistance, and the latter is formed through electrostatic spraying process. Continuous and dense coating with excellent protective performance. At the same time, in conjunction with the sacrificial anode cathodic protection method, zinc alloy or magnesium alloy sacrificial anodes are installed on the channel steel frame. The anode metal is more active than steel, and oxidation reaction occurs first, thereby protecting the channel steel frame from corrosion. In addition, additional sealing treatment should be carried out on the connection parts, welds and other corrosion-prone areas of the channel steel frame to prevent seawater from infiltrating, so as to comprehensively improve the corrosion resistance of the channel steel frame in the marine environment.
In high-temperature environments, such as steel mills and boiler rooms, channel steel frames not only have to withstand high temperatures, but may also face high-temperature oxidation and thermal corrosion. At this time, it is necessary to use high-temperature anti-corrosion coatings, such as silicone high-temperature resistant coatings, which can form a stable protective film in a high-temperature environment of 200-600℃ to prevent steel oxidation. Before painting, high-temperature curing treatment of the channel steel frame can further enhance the bonding strength between the coating and the steel. In addition, the structure of the channel steel frame should be reasonably designed to avoid local overheating, and heat dissipation measures should be added, such as installing heat sinks or ventilation devices, to reduce the surface temperature of the steel, and slow down the damage of high temperature to the anti-corrosion coating, so as to ensure the normal use and anti-corrosion performance of the channel steel frame in high-temperature environments.
When the channel steel frame is used in an underground environment, it will be corroded by moisture, microorganisms, acids, alkalis, salts and other substances in the soil. To this end, the channel steel frame must first be treated with an external anti-corrosion coating. Polyethylene adhesive tape or fused bonded epoxy powder (FBE) coating can be used. The former has good flexibility and impact resistance and can adapt to soil deformation; the latter has excellent adhesion and chemical corrosion resistance. At the same time, the impressed current cathodic protection method is used to apply cathodic current to the channel steel frame by burying auxiliary anodes and reference electrodes, making it a cathode, thereby inhibiting corrosion. In addition, during the construction process, it is necessary to ensure that the air permeability and drainage of the soil around the channel steel frame are good to avoid the aggravation of microbial corrosion due to water accumulation and anoxic environment.
In actual applications, channel steel frames often face the combined effects of multiple environmental factors, such as areas with high humidity and industrial pollution. In this case, a composite protection system needs to be constructed. Combined with the protection points of different environments, a variety of protection technologies are used to work synergistically, such as combining high-performance anti-corrosion coatings with cathodic protection. At the same time, special protection measures are added for special environmental factors, such as installing protective sleeves in parts susceptible to mechanical damage, and increasing the wear resistance and anti-fouling properties of the coating in areas with severe pollution. In addition, a real-time monitoring system is established to dynamically monitor the corrosion of the channel steel frame, promptly identify potential problems and take repair measures. Through this comprehensive, multi-level composite protection system, the anti-corrosion and anti-rust performance of the channel steel frame is maximized to ensure its long-term stable operation.
