Seeking advice on SY/T0088-2016 \"Technical Standards for Cathodic Protection of the Outer Wall at the Bottom of Steel Storage Tanks\"
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The last edit to this post was made by A calm mindset HAPPY on 2022-4-11 at 12:02. SY/T0088-2016, the \"Technical Standard for Cathodic Protection of the Outer Wall at the Bottom of Steel Storage Tanks\", stipulates that when the diameter of the storage tank is greater than 18 meters, or when the soil resistivity is 100 ohm·m or higher, forced current cathodic protection should be used. What is the reason for such a regulation? Is cathodic protection not required if it’s less than 18m? Also, are austenitic stainless steel storage tanks protected by cathodic protection? Thank you!
Since the corrosion of the inner walls at the bottom of crude oil tanks and sewage tanks is primarily caused by electrochemical corrosion and bacterial corrosion resulting from crude oil deposits and sewage, and the crude oil deposits and sewage at the tank bottom have a high salt content and high temperature, their corrosive nature is quite strong. Currently, the sacrificial anode method is widely used for cathodic protection of the inner wall of storage tank bottoms. This approach ensures the safety and reliability of the tanks, requires no dedicated maintenance personnel, and provides excellent protection. Materials commonly used as sacrificial anodes include magnesium and magnesium alloys, zinc alloys, aluminum alloys, etc. The anode blocks are evenly arranged on the bottom plate inside the storage tank, with the steel plates being directly welded to the anode blocks.
Why doesn’t the standard recommend cathodic protection for small tanks? Is the cost-performance ratio not suitable? Is cathodic protection only applicable to carbon steel storage tanks? Is this problem not an issue for stainless steel?
The standards state that forced current cathodic protection is advisable when the diameter is greater than 18 meters. It’s not that cathodic protection is not recommended for smaller tanks; rather, forced current cathodic protection is not recommended in such cases, while sacrificial anode cathodic protection is advised.
Due to the use of sacrificial anode blocks, the cathodic protection current density does not meet the requirements for achieving the desired protection voltage. This applies to steel tanks, that is, ordinary carbon steel; it is not suitable for stainless steel, as a passive film easily forms on the surface of stainless steel@yeathchen