There are currently cast iron, steel, aluminum, and copper heat exchangers available. In terms of heat dissipation performance, copper and aluminum are better, followed by steel and cast iron. When choosing a heat exchanger, the first thing to consider is the material. Because the material determines its safety, reliability, and lifespan. When purchasing, it is required to provide a test report on whether the material is corroded and how high its compressive strength is. There are several major misconceptions during the purchasing process.
Misconception 1: Does an aluminum heat exchanger not corrode?
Due to the different corrosion principles of materials, although aluminum heat exchangers are not afraid of acid corrosion (oxidation corrosion), they are prone to alkali corrosion and chloride ion corrosion. Therefore, when the water quality of a heating system is alkaline (pH value above 7) or has a high chloride ion content (high salt content), there is a risk of corrosion and water leakage in the heat exchanger.
Due to the poor welding performance of aluminum alloys, consumers avoid using aluminum alloy heat exchangers with welds and instead choose fully die cast aluminum alloy heat exchangers to prevent property damage caused by water leakage at the welds. In addition, experts remind consumers to avoid installing aluminum alloy heat exchangers mixed with other materials because the water quality requirements for aluminum alloy heat exchangers are different from those for steel.
Misconception 2: Are Wall Thicknesses Afraid of Corrosion?
Cast iron heat exchangers are not easily corroded or damaged because cast iron itself has good resistance to oxidation and corrosion, rather than due to wall thickness. In recent years, some small domestic manufacturers have attempted to solve the anti-corrosion problem of steel heat exchangers by increasing the wall thickness, which is completely wrong. Because the corrosion of steel heat exchangers is mainly localized corrosion of small holes, rather than uniform corrosion of spiral plate heat exchangers. In recent years, due to the continuous improvement of the manufacturing process of heat exchangers, the industry's requirements have become increasingly high. Cast iron heat exchangers, due to their low pressure, heavy volume, rough appearance, and high production energy consumption, have many insurmountable disadvantages and will gradually be eliminated from the market.
Misconception 3: Not afraid of corrosion without welds or smooth inner walls?
The absence of welds or smooth inner walls does not mean that there is no corrosion.
Misconception 4: Will copper heat exchangers be corroded?
The new type of steel heat exchanger is now widely used in home decoration in northern China. And anti-corrosion is the highlight of this year's heat exchanger market. In fact, heat exchangers all have anti-corrosion issues. If ordinary steel heat exchangers are not treated with anti-corrosion, they are afraid of oxidation and corrosion. When stopping heating, they must be filled with water and sealed for maintenance to prevent air from entering; Aluminum is afraid of alkaline water corrosion. Generally speaking, copper has better corrosion resistance than steel, but in certain environments, copper heat exchangers can also corrode. For example, if there is sludge, excessive sulfur content, or carbon attached to the surface of the selected copper in the system, it can cause corrosion of copper heat exchangers.
Misconception 5: Is internal coating anti-corrosion?
At present, the commonly used coatings for anti-corrosion inside heat exchangers in China are divided into two categories. One type of coating is organic coating, and currently most domestic brands on the market use these two types of organic coatings for heat exchangers. This coating mainly achieves corrosion prevention by isolating and preventing direct contact between water and the substrate. However, the coating and the body are bonded together like glue (physical bonding), requiring high surface treatment of the substrate, otherwise the coating is prone to peeling off, which is a defect of organic coatings. Another type is inorganic coatings, represented by zinc based chromium salts. The coating and substrate chemically bond at high temperatures, with strong adhesion and resistance to peeling. But its process requirements are strict, and the quality of its coating can only be guaranteed by strictly controlling various process parameters. Some manufacturers, in order to save costs, skip certain processing steps and only perform one internal coating treatment, with a coating thickness generally not exceeding 30 microns. Therefore, many heat exchangers on the market that have been coated with an inner layer experience large areas of bubbling after soaking in hot water for about 5 days, causing the coating to peel off and the substrate to rust. Consumers should be cautious when choosing anti-corrosion heat exchangers.
The heat exchanger heating system has the characteristics of high technical content, long service life, and easy to cause associated losses when problems occur. Therefore, the installation quality and after-sales service of the heat exchanger are crucial. Standardized installation is also an issue to pay attention to after purchasing a heat exchanger. When consumers purchase heat exchangers and accessories, they should not be tempted by cheap prices and choose small businesses or brands without credit guarantees, or go to street shops. Instead, they should choose strong large enterprises and famous brand products and not install them themselves. The purchase location should be chosen at the manufacturer, and the heat exchanger manufacturer should come to the site for installation to ensure that the long-term interests of consumers are not harmed.
