Corrosion fatigue is a common and dangerous failure mode of pressure vessels during long-term operation. It is caused by the accumulation of damage to materials under the combined action of corrosive environments and alternating stress. Since many pressure vessels operate in high-temperature, high-pressure, acidic/alkaline, or chlorine-containing environments, the coupling effect of corrosion and fatigue significantly reduces the strength and lifespan of the materials. Therefore, in-depth research into the influence mechanism of corrosion fatigue is of great significance for ensuring the safe operation of pressure vessels. As a driver of technological innovation in the industry, FRHE has always focused on the material properties, structural design, and application scenarios related to corrosion fatigue, continuously improving product durability and safety to provide more reliable technical support for various pressure vessels.

The essence of corrosion fatigue is the localized corrosion of the material surface under the action of corrosive media, making cracks easier to initiate and propagate. When a pressure vessel is subjected to periodic pressure changes, alternating stress continuously acts on the tiny corrosion defects on the material surface, promoting rapid crack initiation. Because corrosion weakens the protective film on the material surface, exposing the metal to the medium, the critical stress for crack initiation decreases significantly. Compared to simple mechanical fatigue, corrosion fatigue has a lower critical cycle number and a faster crack propagation rate.

During the crack propagation stage, the mutually reinforcing effect of corrosion and fatigue is particularly pronounced. Fatigue loading causes the crack tip to open and close continuously, accelerating the penetration of corrosive media into the crack interior; the corrosive media further dissolves the metal at the crack tip, making its geometry sharper and leading to increased stress concentration. This vicious cycle causes the crack propagation rate to increase exponentially, ultimately leading to sudden material fracture. The corrosion fatigue effect is particularly pronounced in environments containing chloride ions, sulfides, or high humidity, significantly shortening the lifespan of pressure vessels.

Material properties are also a crucial factor influencing corrosion fatigue. While high-strength steel has higher load-bearing capacity, it is generally more sensitive to corrosion and its durability under corrosion fatigue conditions is inferior to that of low-strength steel. Furthermore, welded areas, due to their inhomogeneous microstructure and residual stress, are more prone to becoming weak points in corrosion fatigue. Therefore, welded areas are typically one of the main sites for corrosion fatigue cracking in pressure vessels.

Corrosion fatigue is a highly insidious and hazardous form of pressure vessel failure. Its influencing mechanisms include corrosion-induced crack initiation, corrosion-accelerated crack propagation, and the coupling effect of material properties and stress state. By selecting appropriate materials, optimizing design, improving media control, and strengthening operational monitoring, the risk of corrosion fatigue can be effectively reduced, ensuring the long-term safe operation of pressure vessels.