Corrosion condition of the inner wall surface at the top of the atmospheric and vacuum distillation stripping tower in petrochemical industries

In the petrochemical industry, corrosion of the inner wall at the top of vacuum towers is usually caused by the temperature and pressure of the operating environment, as well as the chemical properties of the medium. Specific to the situation you described, the material of the tower is 16MnR, and this material is prone to erosion by media under high-temperature and full-vacuum conditions. Pitting corrosion may be caused by the presence of more corrosive components in the medium, or by insufficient local protection at the top of the tower. Given that the tower has been in use for over two years, this corrosion could be normal wear and tear, but it may also indicate more serious problems. It is recommended to conduct a thorough inspection, particularly carrying out detailed material and structural tests on the corroded areas of the inner wall at the top of the tower, to ensure safe operation. If necessary, considering replacing the damaged part or the entire tower top, or using more suitable materials to prevent future corrosion, is an option. .

Definition of pitting corrosion: Pitting corrosion, also known as pit corrosion, is a highly localized form of corrosion that typically occurs in small areas on the metal surface. This form of corrosion causes small, deep holes to form on the surface of metal materials; these holes are sometimes difficult to detect even with the naked eye. Pitting corrosion typically occurs on the surfaces of metals or alloys that are prone to passivation, such as stainless steel, aluminum alloys, and titanium alloys. When these materials are exposed to chloride-containing solutions or other specific corrosive media, the passivation film may break at certain defect sites, leading to rapid corrosion in those local areas. 2 Characteristics of pitting corrosion The main characteristics of pitting corrosion include high concealment and rapid development. Once pitting corrosion begins, the corrosion pits expand rapidly to great depths. In addition, pitting corrosion also has the following characteristics: Localization: Pitting corrosion usually occurs in small areas, with the surrounding areas remaining largely unaffected. Concealment: Since pitting corrosion occurs beneath the surface, it is usually not easy to detect until the corrosion pits penetrate the material or become visible. Rapid development: Pitting corrosion can cause material perforation in a short period of time, especially in favorable corrosion environments. Induction of stress concentration: Pitting holes often become areas of stress concentration, which can lead to a significant decline in the structural integrity and mechanical properties of the material. Electrochemical properties: Pitting corrosion typically occurs in environments containing inert ions such as chloride ions, which can destroy the metal’s passivation layer and trigger localized corrosion.