**Abstract:**
Corrosion damage in mechanical seals is a common issue that significantly affects their performance and lifespan. This damage primarily occurs in four main areas: corrosion of metal rings, non-metallic rings, auxiliary seals, and the contact surfaces between these components. To mitigate such damage, several protective measures are commonly applied, including proper material selection, optimized structural design, and regular maintenance during operation. Understanding the mechanisms of corrosion is essential for improving the reliability and efficiency of mechanical seals.
**Keywords:** mechanical seal; corrosion; protection method; wear; sealing
Mechanical seals are widely used in pumps, compressors, and other rotating equipment, but they are prone to various types of damage, including corrosion, thermal stress, and mechanical wear. Among these, corrosion is often the most critical and difficult to manage. Due to their complex structure and exposure to harsh environments, mechanical seals can suffer from multiple forms of corrosion, which can lead to leakage, reduced efficiency, and even catastrophic failure if not addressed promptly.
**1. Corrosion in Mechanical Seals**
**1.1 Corrosion of Metal Rings**
Metal rings in mechanical seals are typically made of materials like stainless steel, cobalt alloys, or chrome-based metals. However, these materials can still be vulnerable to corrosion when exposed to aggressive media. One common form is uniform surface corrosion, where the entire surface of the ring is affected. This can lead to early wear, leakage, and noise. In some cases, the corrosion is more severe when a protective oxide layer (passivation film) is damaged due to friction or improper operating conditions, increasing the risk of galvanic corrosion.
Another serious type is stress corrosion cracking (SCC), which occurs when a metal is subjected to both tensile stress and a corrosive environment. This leads to the formation of cracks at weak points on the surface, which can propagate and eventually cause the ring to fail. Materials such as hardfaced alloys, cast iron, and carbides are particularly susceptible to SCC. Cracks in the sealing ring usually spread radially and can result in increased leakage and accelerated wear.
**1.2 Corrosion of Non-Metallic Rings**
Non-metallic rings, such as those made of graphite or PTFE (polytetrafluoroethylene), are also prone to corrosion, especially in chemical environments. For example, impervious graphite rings, which are often impregnated with resin to enhance their properties, can degrade when exposed to high temperatures or incompatible chemicals. If the temperature exceeds 180°C, the resin may decompose, reducing the ring’s wear resistance. Additionally, poor material selection can lead to chemical reactions that weaken the structure of the ring.
Oxidation is another concern for graphite rings, particularly in oxidizing environments. When the end face becomes dry or poorly cooled, temperatures can rise to 350–400°C, causing the graphite to react with oxygen and produce gases like CO. This can lead to surface roughening or even fracture of the ring. Similarly, polytetrafluoroethylene (PTFE) rings, which are often reinforced with glass fiber, graphite, or metal powders, can suffer from selective corrosion of the fillers. For instance, in hydrofluoric acid, the glass fibers may degrade thermally, compromising the integrity of the seal.
To prevent these issues, it is crucial to implement proper cooling systems, select appropriate materials based on the operating environment, and ensure deep impregnation of resins in graphite rings. Regular inspection and maintenance are also key to identifying early signs of corrosion and preventing further damage.
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