Stress corrosion cracking occurs in the weld seams and heat-affected zones of oil-containing wastewater storage tanks in the petrochemical industry; what methods can be used to address this issue?
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As this tank is mainly used to store oily wastewater. If a conventional coating is used for corrosion protection inside the tank, it causes significant damage. In some cases, the coating developed problems within less than a year – bulging, hardening, and damage – failing to serve as an anti-corrosion coating. The operating conditions in sewage tanks are relatively harsh; the main substances involved in operations include raw water containing H2S and NH3, as well as various other substances such as CO2, CN-, phenols, and oils. The temperature of the sewage is ≤60°C. When carbon steel operates under such conditions, its metal surface suffers significant corrosion, as shown in the figure below. Its form of corrosion is electrochemical corrosion; in particular, stress corrosion cracking tends to occur at the joints and gaps in the tank wall plates, as well as at welds and where the metal base material is subjected to bending forces. At the same time, uniform corrosion of the metal surface occurs. What method can be used to solve the problem.
To address the problem of stress corrosion cracking in the weld seams and heat-affected zones of storage tanks containing petroleum-based wastewater, the following methods can be considered: 1. **Use of corrosion-resistant materials**: It is possible to use more corrosion-resistant materials for manufacturing or repairing these tanks, such as stainless steel and duplex steel, which are capable of withstanding various corrosive agents present in oily wastewater. 2. **Add an anti-corrosion coating**: Use high-performance anti-corrosion coatings suitable for harsh environments, such as epoxy coatings and polyurethane coatings; these coatings provide stronger protection by preventing corrosive agents from coming into direct contact with the metal surface. 3. **Apply cathodic protection**: Slow down or prevent the corrosion of the tank by applying an external current or using a sacrificial anode. 4. **Regular maintenance and inspection**: Regularly inspect the welds and heat-affected zones of the storage tanks, and address any corrosion or cracks detected promptly to prevent problems from worsening. 5. **Optimized design and construction**: During the design and construction of storage tanks, avoid using excessive welding joints, minimize stress concentration points, and ensure the quality of welds. Through the combined use of the above methods, stress corrosion cracking in storage tanks for oily wastewater in the petrochemical industry can be effectively addressed and prevented. .