How to prevent corrosion of the low-pressure wet-type gas holder with petrochemical spiral guides?

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This post was last edited by Wang Wei2 on 2020-6-4 at 15:52. How to prevent corrosion in petrochemical spiral-guided low-pressure wet gas tanks? Usage overview: In petrochemical gas fractionation units, the gas tanks that were commonly used in the past were spiral-guided low-pressure wet gas tanks, which consist of a water tank, two intermediate sections, and a dome. The main material is carbon steel. Its working principle is that the middle section and the bell cover are located in a tank, where they can rise and fall freely under certain conditions to change the air storage volume. As the middle section and bell cover are frequently submerged in water and then rise to the surface, they suffer severe corrosion due to the long-term exposure to harmful substances such as gas, water, and chemical atmospheres. Although protective measures were taken on the surface, issues with the materials used for protection and the quality of the installation led to significant portions of the tank’s wall panels becoming corroded, perforated, or cracked within less than 5 years of operation, forcing the tank to be scrapped. Corrosion condition of the gas holder: In a petrochemical company’s 10,000 cubic meter spiral-guided low-pressure wet gas holder, after more than a year of operation, the surface coating began to fade and blister, with rust spots appearing in some areas. In less than two years, the surface coating started to peel off in parts of the middle section and the dome, leading to corrosion of the exposed metal surface. It is mainly characterized by ulcerative corrosion on the outer surface of the mid-section, with corrosive spots and pits appearing on the surface; these are particularly common near the waterline (above and below the water line after the mid-section is fully raised). The depth of the corrosion is about 2 mm, and iron oxide rust with a thickness of approximately 4–5 mm is present in the corroded areas. Upon stopping the brushing inspection, it was found that most of the original red lead anti-rust paint and coal tar pitch on the inner wall had peeled off. A uniform layer of corrosion rust appears on the inner surface of the bell jar, while the steel structure on the outer surface of the gas tank is severely corroded; the paint coating on its surface is damaged, and there are many rusty spots on the metal surface. Several cracks appeared near the weld seams of the middle section and the bell cover guide rails; some of the middle sections were deformed, which affected the normal operation of the gas holder. Furthermore, due to the presence of harmful substances in the gas, large amounts of impurities such as sulfides end up in the water, worsening its quality and causing the surface to turn black and emit an unpleasant odor. Due to such water quality in the tank, it causes more severe corrosion of the gas holder. Corrosion prevention measures: How to prevent corrosion in such gas tanks?