Spiral heat exchangers are widely used in the chemical, pharmaceutical, food processing, and energy sectors due to their compact structure and efficient heat transfer. Their core performance and service life are largely determined by the material selection. Different operating conditions require tailored materials to ensure corrosion resistance, strength, and cost-effectiveness.
Carbon steel and low-alloy steel are the foundational materials for spiral heat exchangers, suitable for non-corrosive or mildly corrosive media (such as water-to-water heat exchange). These materials offer low cost and high mechanical strength, but require surface treatment (such as galvanizing or coating) to extend their service life. In high-temperature and high-pressure applications, low-alloy steels (such as Q345R) can improve creep and oxidation resistance due to the addition of elements such as molybdenum and chromium.
Stainless steels (such as 304 and 316L) are the mainstream choice for stainless steel spiral heat exchangers, particularly suitable for media containing chloride ions, acids and bases, or sanitary conditions. 316L, due to its molybdenum content, offers superior resistance to pitting and crevice corrosion and is commonly used in the pharmaceutical and food industries. Duplex stainless steels (such as 2205) combine high strength with resistance to chloride stress corrosion, making them suitable for high-temperature fluids containing chloride ions.
Nickel-based alloys (such as Hastelloy C276 and Inconel 625) are designed for use in extremely corrosive environments, such as strong acids (sulfuric acid and hydrochloric acid), high-temperature and high-pressure hydrogen, or desalination systems. While expensive, these materials resist intergranular corrosion and high-temperature oxidation and are often used in high-end applications such as petrochemicals and environmental protection.
Titanium is an ideal choice for seawater heat exchangers. Due to its excellent chloride ion corrosion resistance and lightweight design, it is widely used in applications such as ships and coastal power plants. Furthermore, non-metallic materials such as graphite and ceramics, while highly corrosion-resistant, are also brittle and are therefore limited to small-scale, specialized applications.
Material selection requires a comprehensive consideration of medium characteristics, temperature, pressure, and cost. Designers of spiral heat exchangers need to balance performance and economy through corrosion testing and engineering experience to ensure long-term and stable operation of the equipment.
