Corrosion causes of seamless steel pipes

If seamless steel pipes become corroded, it can significantly affect their functionality and increase economic costs. Corrosion in seamless steel pipes can be classified into four main types, each with distinct characteristics and implications. Here's a detailed introduction to these types.

1. Intergranular Corrosion

Intergranular corrosion occurs along the grain boundaries, destroying the connections between the crystals. This type of corrosion is particularly harmful as it can make the seamless steel pipe brittle or reduce its compressive strength, potentially leading to safety accidents. Martensitic seamless steel pipes are especially susceptible to this type of corrosion due to differences in the electrode potential caused by variations in composition or ground stress in the dislocation areas.

2. Uniform Corrosion

Uniform corrosion affects the entire surface of the seamless steel pipe exposed to a corrosive environment, causing chemical changes and uniform material degradation. This type of corrosion allows for accurate measurement of its rate and prediction of its extent, enabling the setting of safety performance and lifespan expectations. Uniform corrosion is generally not considered highly risky since it can be measured and managed by monitoring the reduction in pipe thickness and quality. In normal environments, the uniform corrosion rate of seamless steel pipes is low, resulting in long service life and minimal maintenance requirements.

3. Pitting Corrosion

Pitting corrosion refers to localized damage that occurs on specific areas of the seamless steel pipe's surface. This type of corrosion can rapidly develop into deep pits, potentially penetrating through the pipe. Pitting corrosion is especially dangerous for high-pressure vessels. Once detected, affected areas should be promptly polished or painted to prevent further corrosion.

4. Fatigue Corrosion

Fatigue corrosion involves the deterioration of seamless steel pipes under the combined effects of corrosive substances and alternating stress. This type of damage is characterized by the presence of corrosion pits and numerous cracks, which significantly reduce the fatigue limit of the steel pipes and lead to premature failure. Unlike mechanical fatigue, corrosion fatigue does not have a definite fatigue strength, and the fatigue limit decreases with increased cyclic loading.

Understanding these types of corrosion and their implications is crucial for maintaining the integrity and safety of seamless steel pipes in various applications. Proper preventive measures and timely maintenance can mitigate the adverse effects of corrosion and extend the service life of the pipes.