Five misunderstandings in the purchase of heat exchangers
Myth 1: Does the aluminum heat exchanger not corrode?
Due to the different corrosion principles of materials, although aluminum heat exchangers are not afraid of acid corrosion (oxidative corrosion), they are prone to alkali corrosion and chloride ion corrosion. Therefore, when the water quality of a heating system is alkaline (pH value is higher than 7), or the chloride ion content is high (salt content is high), the heat exchanger has the hidden danger of corrosion and water leakage. Due to the poor welding performance of aluminum alloys, consumers avoid using aluminum alloy heat exchangers with welded seams, and choose fully die-cast aluminum alloy heat exchangers to avoid property damage caused by water leakage at the welded seams. In addition, experts remind consumers: Since the requirements for water quality of aluminum alloy heat exchangers are different from those of steel, it is best to avoid the mixed installation of aluminum alloy heat exchangers with other materials.
Misunderstanding 2: Is the wall thickness afraid of corrosion?
The cast iron heat exchanger is not easy to be damaged by corrosion, because the cast iron itself has good oxidation and corrosion resistance, not because of the wall thickness. In recent years, some small manufacturers have tried 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 localized corrosion of small holes, rather than uniform corrosion of spiral plate heat exchangers. In recent years, due to the continuous improvement of the heat exchanger manufacturing process, the industry requirements are getting higher and higher. Market eliminated.
Misunderstanding 3: There is no weld or the inner wall is smooth and not afraid of corrosion?
The absence of welds or smooth inner walls does not mean there is no corrosion.
Myth 4: Will the copper heat exchanger be corroded?
The new steel heat exchanger has been widely used in home decoration nowadays. And anti-corrosion is the highlight of the heat exchanger market this year. In fact, heat exchangers have corrosion problems. If the ordinary steel heat exchanger is not treated with anti-corrosion treatment, it is afraid of oxidation and corrosion. It must be filled with water for airtight maintenance when heating is stopped to prevent air from entering; while the aluminum heat exchanger is afraid of alkaline water corrosion. Generally speaking, copper has better corrosion resistance than steel, but under certain circumstances, copper heat exchangers will also corrode. For example, if there is sludge in the system, excessive sulfur content, or the selected copper surface has carbon attached It will cause corrosion of copper heat exchangers.
Misunderstanding 5: Internal coating is anti-corrosion?
At present, the commonly used coatings for internal corrosion protection of heat exchangers are divided into two categories. One type of coating is organic coating, and most brands of heat exchangers on the market currently use these two kinds of organic coatings. This coating mainly achieves corrosion protection by isolating and preventing water from coming into direct contact with the substrate. However, the coating and the body are bonded together (physically) similar to glue, which requires high surface treatment of the substrate, otherwise the coating is prone to peeling off, which is the biggest defect of organic coatings. The other type is inorganic coatings, represented by zinc-based chromium salts. The coating and the substrate are chemically combined at high temperature, with strong adhesion and not easy to peel off.