Corrosion and Measures to Prevent Corrosion in Oil Storage Tanks
As the economy advances, widespread car ownership has spurred the growth of the oil industry. To store oil for future use, oil storage tanks are commonly employed due to the immediate impracticality of utilizing freshly extracted oil. The corrosion level in these tanks significantly impacts the petroleum industry's progress. Unfortunately, corrosion is a prevalent issue in operational oil storage tanks, necessitating anti-corrosion measures. This is essential to prevent wall perforation, ensuring the safety of both property and lives associated with oil storage.
Usage of oil storage tanks and causes of easy corrosion
Oil storage tanks are pivotal in China's petroleum industry, widely utilized by oil fields, refining companies, and production bases. They come in two types—floating roof tanks and dome tanks—and are categorized by size: small, medium, large, and extra-large. Typically used in oil fields, dome tanks store crude oil based on quantity. Additionally, some refineries use oil storage tanks for chemical-laden sewage. Due to the corrosiveness of stored liquids, these tanks have a consumable classification with a general lifespan of around 5 years. Proper anti-corrosion measures can extend this lifespan. Corrosion is primarily caused by corrosive impurities such as hydrogen and sulfur compounds in the stored liquid, exacerbated by external environmental factors. Consequently, China is actively researching measures to prevent corrosion in oil tanks.
Corrosion-prone parts of oil storage tanks
1. Outer Wall of Oil Storage Tanks
Currently, the outer wall of oil storage tanks is highly susceptible to corrosion, primarily influenced by external environmental factors. Prolonged exposure to sunlight exacerbates the corrosion level. In refinery environments, chemical gases contribute to outer wall corrosion, while proximity to the sea subjects the outer wall to atmospheric corrosion. The corrosive impact intensifies in humid southern cities, where water molecules in the air form a film on the metal surface, leading to electrolysis and chemical reactions that corrode the outer wall.
2. Inner Wall of Oil Storage Tanks
With the exception of the top portion not in direct contact with oil, the remaining parts of the inner wall are in constant contact with stored oil. The bottom of the inner wall experiences the most severe corrosion, followed by the top area. Different liquids stored in the tank, including water, acid, alkali, and salt, contribute to electrolytic water formation on the inner wall, causing corrosion and potentially leading to leaks. Uneven oxygen concentration at the tank's top results in corrosion, exacerbated by chemical reactions in the mixed gas produced in the air gap.
3. External Bottom of Oil Storage Tanks
Typically buried underground, the external bottom of large oil storage tanks is highly vulnerable to corrosion. Insufficient oxygen concentration in the soil can lead to battery corrosion. Chemical reactions involving soil water and air, as well as exposure to open-air elements like rain and snow, induce electrochemical responses at the tank bottom, causing corrosion.
Basic measures for anticorrosion of oil storage tanks
1. Uniform Application of Anticorrosive Materials on the Outer Wall
When conducting anti-corrosion procedures on the external surface of oil storage tanks, it's essential to apply coatings with outstanding resistance to oil and fouling. These coatings facilitate subsequent maintenance and re-painting. Moreover, for oil storage tanks exposed to prolonged sunlight, the selected anti-corrosion materials for the outer wall should possess sun-blocking properties and temperature adaptability. Opt for materials that resist peeling and are less susceptible to sun-induced steam, such as dark anti-corrosion coatings. Additionally, consider the fire resistance and expansion capabilities of the anti-corrosion coating. This type of coating not only prevents corrosion and minimizes heat radiation but also mitigates temperature to prevent combustion due to excessive heat. Simultaneously, it represents an eco-friendly and pollution-free anti-corrosion solution.
2. Internal Coating
When addressing the inner wall in direct contact with oil, distinct anticorrosive measures should be employed for various sections.
(1) Utilize an impermeable coating for the bottom of the inner wall to mitigate medium corrosion. Alternatively, a high-potential coating can be applied, using a conductive material to prevent iron from becoming an anode.
(2) Apply a resistive film with a resistivity of approximately 10^6 ohms for the roof area of the inner wall. This helps prevent the aggregation of static electricity. The chosen anticorrosive coating should effectively inhibit corrosion caused by chemical gases. Ensure the coating does not contaminate oil products.
(3) For other inner walls in contact with oil, in addition to using the mentioned resistive film, it is crucial to ensure that the selected anticorrosive coating does not harm the inner wall steel or pollute oil products. This precaution prevents steel corrosion originating from the coating itself.
3. Enhance the Environment at the Base of the Exterior Wall
When conducting anti-corrosion measures on the lower section of the oil storage tank's outer wall, the following three approaches can be employed:
(1) Enhance the soil conditions at the base of the outer wall. Optimal burial in sandy soil helps with water retention, effectively reducing corrosion on the lower section of the outer wall. The application of cement on the ground surface creates a cement field, reducing rainwater and other moisture infiltration into the soil, as illustrated in Figure 1.
(2) Expand the protective layer coverage. The addition of substances containing polyethylene, such as glass fiber and plastic bags, reinforces the protective layer.
(3) Implement cathodic protection. Cathode protection addresses insufficient protective layer issues, ensuring the integrity of underground structures and providing preventive measures against damage.
Fig. 1 Oil storage tanks placed in cement ground
The corrosion of oil storage tanks significantly impacts oil enterprises. In the absence of anti-corrosion measures, oil leakage poses a threat to the life safety of individuals in the vicinity. Recognizing this, our country places significant emphasis on the anti-corrosion measures for oil storage tanks. As science and technology continue to advance, future improvements in anti-corrosion technology for oil storage tanks are anticipated. Technicians will persistently innovate and address this issue through practical solutions, ensuring comprehensive protection of lives and property and contributing to the stable development of the oil industry.
Usage of oil storage tanks and causes of easy corrosion
Oil storage tanks are pivotal in China's petroleum industry, widely utilized by oil fields, refining companies, and production bases. They come in two types—floating roof tanks and dome tanks—and are categorized by size: small, medium, large, and extra-large. Typically used in oil fields, dome tanks store crude oil based on quantity. Additionally, some refineries use oil storage tanks for chemical-laden sewage. Due to the corrosiveness of stored liquids, these tanks have a consumable classification with a general lifespan of around 5 years. Proper anti-corrosion measures can extend this lifespan. Corrosion is primarily caused by corrosive impurities such as hydrogen and sulfur compounds in the stored liquid, exacerbated by external environmental factors. Consequently, China is actively researching measures to prevent corrosion in oil tanks.
Corrosion-prone parts of oil storage tanks
1. Outer Wall of Oil Storage Tanks
Currently, the outer wall of oil storage tanks is highly susceptible to corrosion, primarily influenced by external environmental factors. Prolonged exposure to sunlight exacerbates the corrosion level. In refinery environments, chemical gases contribute to outer wall corrosion, while proximity to the sea subjects the outer wall to atmospheric corrosion. The corrosive impact intensifies in humid southern cities, where water molecules in the air form a film on the metal surface, leading to electrolysis and chemical reactions that corrode the outer wall.
2. Inner Wall of Oil Storage Tanks
With the exception of the top portion not in direct contact with oil, the remaining parts of the inner wall are in constant contact with stored oil. The bottom of the inner wall experiences the most severe corrosion, followed by the top area. Different liquids stored in the tank, including water, acid, alkali, and salt, contribute to electrolytic water formation on the inner wall, causing corrosion and potentially leading to leaks. Uneven oxygen concentration at the tank's top results in corrosion, exacerbated by chemical reactions in the mixed gas produced in the air gap.
3. External Bottom of Oil Storage Tanks
Typically buried underground, the external bottom of large oil storage tanks is highly vulnerable to corrosion. Insufficient oxygen concentration in the soil can lead to battery corrosion. Chemical reactions involving soil water and air, as well as exposure to open-air elements like rain and snow, induce electrochemical responses at the tank bottom, causing corrosion.
Basic measures for anticorrosion of oil storage tanks
1. Uniform Application of Anticorrosive Materials on the Outer Wall
When conducting anti-corrosion procedures on the external surface of oil storage tanks, it's essential to apply coatings with outstanding resistance to oil and fouling. These coatings facilitate subsequent maintenance and re-painting. Moreover, for oil storage tanks exposed to prolonged sunlight, the selected anti-corrosion materials for the outer wall should possess sun-blocking properties and temperature adaptability. Opt for materials that resist peeling and are less susceptible to sun-induced steam, such as dark anti-corrosion coatings. Additionally, consider the fire resistance and expansion capabilities of the anti-corrosion coating. This type of coating not only prevents corrosion and minimizes heat radiation but also mitigates temperature to prevent combustion due to excessive heat. Simultaneously, it represents an eco-friendly and pollution-free anti-corrosion solution.
2. Internal Coating
When addressing the inner wall in direct contact with oil, distinct anticorrosive measures should be employed for various sections.
(1) Utilize an impermeable coating for the bottom of the inner wall to mitigate medium corrosion. Alternatively, a high-potential coating can be applied, using a conductive material to prevent iron from becoming an anode.
(2) Apply a resistive film with a resistivity of approximately 10^6 ohms for the roof area of the inner wall. This helps prevent the aggregation of static electricity. The chosen anticorrosive coating should effectively inhibit corrosion caused by chemical gases. Ensure the coating does not contaminate oil products.
(3) For other inner walls in contact with oil, in addition to using the mentioned resistive film, it is crucial to ensure that the selected anticorrosive coating does not harm the inner wall steel or pollute oil products. This precaution prevents steel corrosion originating from the coating itself.
3. Enhance the Environment at the Base of the Exterior Wall
When conducting anti-corrosion measures on the lower section of the oil storage tank's outer wall, the following three approaches can be employed:
(1) Enhance the soil conditions at the base of the outer wall. Optimal burial in sandy soil helps with water retention, effectively reducing corrosion on the lower section of the outer wall. The application of cement on the ground surface creates a cement field, reducing rainwater and other moisture infiltration into the soil, as illustrated in Figure 1.
(2) Expand the protective layer coverage. The addition of substances containing polyethylene, such as glass fiber and plastic bags, reinforces the protective layer.
(3) Implement cathodic protection. Cathode protection addresses insufficient protective layer issues, ensuring the integrity of underground structures and providing preventive measures against damage.
Fig. 1 Oil storage tanks placed in cement ground
The corrosion of oil storage tanks significantly impacts oil enterprises. In the absence of anti-corrosion measures, oil leakage poses a threat to the life safety of individuals in the vicinity. Recognizing this, our country places significant emphasis on the anti-corrosion measures for oil storage tanks. As science and technology continue to advance, future improvements in anti-corrosion technology for oil storage tanks are anticipated. Technicians will persistently innovate and address this issue through practical solutions, ensuring comprehensive protection of lives and property and contributing to the stable development of the oil industry.
