Corrosion of caustic soda storage tank bodies and protective measures

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The materials of caustic soda storage tanks are mainly metallic, and corrosion can be divided into uniform and localized corrosion. Uniform corrosion occurs when the medium inside the metal fails to provide protection, allowing corrosive substances to continuously erode the metal surface, resulting in thinner tank walls and a reduced load-bearing capacity of the tank. Local corrosion includes stress corrosion, pitting corrosion, intergranular corrosion, and abrasion. A certain company uses carbon steel tanks primarily in the production of cleaning agents for heating and storing sodium hydroxide at 60–70°C. In an environment of high temperature + stress corrosion + high alkali concentration, alkali embrittlement is likely to occur. It is common to use anti-corrosion materials for coating in such situations. The coating material for caustic soda tanks is the first step in effectively preventing corrosion; materials with strong resistance to alkalis can be used for this purpose, such as stainless steel and fluorinated coatings. However, it has been found through practical use that the choice of anti-corrosion material has a direct impact on the lifespan of caustic soda storage tanks. Due to the high cost of stainless steel and fluorinated coatings, epoxy resins are generally used for anti-corrosion protection. Yet this material also has significant drawbacks: variations in the resin can affect the adhesion and penetration properties of the coating on the tank surface, leading to phenomena such as shrinkage that can result in cracks on the tank’s surface. Is there a material that possesses high toughness, strong adhesion, low shrinkage, good corrosion resistance, as well as tolerance to high temperatures and strong alkalis? Sorey CMI heavy-duty anti-corrosion material is such a material. Sorey CMI heavy-duty anti-corrosion material boasts excellent properties: in addition to high toughness, strong adhesion, low shrinkage, and good corrosion resistance, it can withstand temperatures above 200°C. Its performance under thermal cycling is also outstanding, with a range from -40°C to 204°C ； The material also has good permeability, which allows for minimizing the absorption of substances by the cargo and ensuring its purity; it is thus suitable for anti-corrosion protection of caustic soda storage tanks. The operation method is also quite simple – it only requires application to the outer surface of the tank. Its actual performance is superior to that of stainless steel, fluorinated coatings, and epoxy resins. The left image in the figure below shows corrosion on the outside of the tank caused by the splashing of sodium hydroxide inside the tank ； Right image: Photo taken two years after using the Sorex CMI corrosion protection coating; no signs of corrosion were observed.