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This post was last edited by HSLJHZ on 2017-9-17 09:57. Analysis and Countermeasures for Welds, Cracks, and Corrosion Leakage in Metal Tanks. Abstract: Carbon nanopolymer material technologies are used to address issues such as weld defects, cracks, and corrosion-related leakage in metal storage tanks in real time, thereby ensuring continuous production and avoiding safety hazards. I. Forms of leakage in metal storage tanks: During the manufacturing process of metal storage tanks, metal sheets are typically welded together using welding techniques to form a cavity structure that meets the required standards, and the welded areas represent the main sources of leakage. Three types of leakage often occur: leakage due to sand holes in the weld, leakage due to cracks in the weld, and leakage due to corrosion of the weld. II. Analysis of welds, cracks, and corrosion leakage in metal storage tanks: During the welding process of metals, the material properties change due to high temperatures and thermal stresses; as a result, the welded areas exhibit different properties compared to other areas under the same conditions, thereby creating potential problem areas. The weldability of metals involves two main types of issues: one is the deterioration in the material properties caused by welding, which results in the welded joint losing its original properties; for example, stainless steel loses its corrosion resistance after welding ； Another type involves defects such as cracks and pores occurring in the base metal of the welded joint or in its vicinity. Cracks affect the safe use of welded parts and represent a very dangerous process defect. Welding cracks occur not only during the welding process; some have a certain incubation period, while others arise during reheating after welding. Welding cracks can be classified in different ways depending on their location, size, causes, and formation mechanisms. Based on the conditions under which cracks form, they can be classified into four categories: thermal cracks, cold cracks, reheat cracks, and layered tearing. When leaks occur in the welds or cracks of equipment, it is often accompanied by corrosion caused by the medium involved, such as leaks in alkali tanks, sulfuric acid tanks, ammonia tanks, and gas cabinets. When selecting materials for medium-metal tanks, the corrosivity of the medium is taken into account. Corrosion is a very complex process that is difficult to completely avoid; its degree varies depending on factors such as temperature and concentration. The main forms of corrosion are as follows: 1. General surface corrosion of the equipment. 2. Local corrosion (pitting corrosion, crevice corrosion, intergranular corrosion, stress corrosion cracking, corrosion fatigue, hydrogen-induced cracking, wear corrosion, delamination corrosion, etc.). 3. Metal alkali embrittlement: “Alkali embrittlement” refers to the cracking that occurs in metal and alloy materials in alkaline solutions as a result of the combined effect of tensile stress and corrosive agents. It is a type of stress corrosion cracking. Carbon steel and low-alloy steel are prone to corrosion and cracking in media such as liquid alkali, nitrates, and liquid ammonia, with intergranular cracks being the common type of crack. The segregation of carbon and nitrogen atoms at grain boundaries or the precipitation of carbides act as obstacles to dislocation movement; these obstacles cause dislocations to accumulate in corrosion grooves or pores at the grain boundaries, and under stress this leads to stress concentration, which can easily develop into sources of intergranular cracks. Factors such as the adsorption of specific elements, the segregation of carbon and nitrogen atoms, and stress concentration can further promote the propagation of metal crack sources. Specific ions in a certain medium can adsorb onto the metal at the bottom of tiny cracks, reducing the energy required for the metal to crack and facilitating the propagation of cracking toward the crack front. Under stress, metals undergo plastic deformation, and cracks expand until the metal breaks. “\"Alkali embrittlement\" can cause cracks to appear in the heated areas on both sides of the welds in equipment, leading to alkali leakage; once leakage occurs, it is difficult to repair the welds. IV. Measures for addressing leaks in metal storage tanks 1. Internal anti-corrosion treatment of metals Using non-metallic materials to coat the interior surfaces of metals is the main method for dealing with corrosion issues; such materials include rubber, epoxy resin, polyurethane, and Sorex polymer materials ； Its excellent comprehensive properties, such as superior heat resistance, corrosion resistance, aging resistance, and strong bonding strength, provide perfect protection for metals. 2. Treatment of weld crack leakage points: Once equipment starts operating, it is difficult to shut it down for maintenance in the event of welds, cracks, corrosion, or leakage. Leakage issues continuously corrode the metal, pose safety risks in production, and increase the hazards of flammability, explosiveness, corrosion, and poisoning. In environments where it is not possible to shut down the equipment for maintenance, using SD2240 and SD7111 for comprehensive leak control is an effective solution. It helps to avoid safety risks associated with working with fire or electricity, as well as prevent additional damage to the metal caused by welding, thereby extending the equipment’s service life. V. Repair and protection of carbon nanopolymer materials 1. Leakage due to weld cracks in sulfuric acid tanks (98%) Sulfuric acid tanks: Leaks exist at the welds between the tank body and the pipelines; the medium is 98% sulfuric acid, the temperature is 15°C, the pressure is 0.03 Mpa, and the material used is carbon steel. 2. Weld crack leakage in the alkaline solution storage tank – Finished product alkaline solution tank: Material: Carbon steel ； Temperature: 40-70℃ ； Medium: 32% sodium hydroxide, corrosion and leakage at the bottom of the tank. 3. Corrosion and leakage at the welds of a gas cylinder – man-type dry gas holder; temperature: 50–60°C; material: carbon steel; thickness: 4 mm. Corrosion has occurred at the weld areas, resulting in holes that cause leakage, with hole diameters of 3–5 mm. 4. Cracking and leakage in the welds of the ammonia tank: The remaining ammonia storage tank contains substances such as ammonia and tar; the temperature is 80–90 degrees Celsius, and there is leakage at the weld areas, due to the internal pressure of the tank. Summary: By utilizing polymer nanomaterials and related technologies, the advantages of these materials such as rapid curing, heat resistance, corrosion resistance, and pressure resistance are fully exploited to effectively address leaks on-site. Especially for on-site treatment of low-temperature and low-pressure equipment pipelines that suffer from issues such as dripping, leaking, seepage, etc., in flammable and explosive environments, it is safer, more convenient, time-saving, and reliable. Without disrupting production, it is possible to stay online and address the leaking areas, thereby meeting the requirements for re-sealing and safe operation, resulting in significant economic benefits.