tank cathodic protection

2022-01-18 09:51
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Scope of application: crude oil storage tanks, waste water treatment tanks, sewage tanks.


The storage tank is a large container composed of tank wall, tank top, tank bottom and accessories to store crude oil or other liquids. The cathodic protection of the storage tank includes internal cathodic protection and external cathodic protection, and sacrificial anodes can generally be used inside the storage tank. For cathodic protection, impressed current cathodic protection can also be used inside the storage tank that requires a longer protection life. For the bottom of the storage tank, it is inconvenient to replace the sacrificial anode and requires a long service life, so the impressed current cathodic protection is generally used.


Inner wall cathodic protection of storage tank >>>


The corrosion of the bottom wall of crude oil storage tanks and sewage tanks is mainly due to electrochemical corrosion, bacterial corrosion, etc. caused by crude oil deposition sewage, and the crude oil deposition sewage at the bottom of the tank has high salt content and high temperature. Therefore, it is more corrosive. At present, the sacrificial anode method is generally used for cathodic protection of the inner wall of the storage tank bottom plate. This method is safe and reliable for the storage tank, does not require special personnel to manage, and has a good protection effect. Materials commonly used as sacrificial anodes include aluminum alloy sacrificial anodes and zinc alloy sacrificial anodes. The anode blocks are evenly arranged on the inner bottom plate of the storage tank, and the anode blocks are directly welded to the steel plate.


Bottom cathodic protection of storage tank >>>


The corrosion of the tank bottom is mainly due to the aging and cracking of the asphalt sand layer at the bottom of the tank. The water in the foundation can penetrate to the bottom of the tank through the cracks, causing corrosion of the bottom plate of the outer wall of the tank; rainwater may pass through the tank along the sidewall of the tank. The gap between the bottom plate and the tar sand penetrates in, forming an oxygen concentration battery between areas with different air permeability, forming a large cathode and a small anode, resulting in a particularly fast local corrosion rate, and crevice corrosion may also form in the gap. autocatalytic effect; stray current corrosion; existence of sulfate-reducing bacteria; unqualified construction quality. All of the above factors may cause corrosion of the bottom plate of the outer wall of the storage tank. At present, the impressed current protection method is generally used to protect the outer wall of the tank bottom. Cathodic protection methods such as MMO anode and mesh anode can be used; small storage tanks can be protected by sacrificial anode cathodic protection. The anode materials that can be used include magnesium alloy sacrificial anode and Zinc alloy sacrificial anode.


External cathodic protection of buried storage tanks >>>




The external cathodic protection of buried storage tanks adopts different methods according to the soil resistivity. In the environment with low soil resistivity, sacrificial anode cathodic protection can be used, and magnesium alloy sacrificial anode and zinc alloy sacrificial anode can be used; Impressed current cathodic protection should be used when the rate is high, MMO anodes and mesh anodes can be used.


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