Petrochemical equipment corrosion types
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The corrosion situation of chemical equipment is very complex, and the corrosion types under different conditions and environments are also different.
Corrosion is divided into metal corrosion and non-metal corrosion according to the type of material. Corrosion is divided into general corrosion and local corrosion according to surface morphology. ； Local corrosion also includes pinhole corrosion, stress corrosion cracking, crevice corrosion, galvanic corrosion, wear corrosion, etc. ； Metal corrosion can be divided into physical corrosion, chemical corrosion, electrochemical corrosion, etc. according to the mechanism. physical corrosion: Destruction of materials due to pure physical effects is generally caused by dissolution and penetration, such as the dissolution of molten metal containers, and the dissolution and penetration of high-temperature molten salts and molten alkali into containers. Chemical corrosion: Destruction caused by direct chemical interaction between metals and non-electrolytes. The corrosion process is a pure oxidation-reduction reaction. The corrosion medium directly collides with the atoms on the metal surface to form corrosion products. No current is generated during the reaction, which complies with the laws of chemical kinetics. electrochemical corrosion: Destruction caused by electrochemical interaction between metal and electrolyte solution. During the reaction process, the anode loses electrons and the cathode gains electrons, as well as the flow of electrons (current). The process conforms to the laws of electrochemical kinetics.
The local corrosion forms of petrochemical equipment mainly include pitting corrosion, intergranular corrosion, stress corrosion, etc. For chemical machinery, the inside of the machinery is susceptible to corrosion by chemical materials, and the outside will be corroded by the external environment during actual use. Moreover, factors such as oxygen, acid and alkali in chemical production are in direct contact with the outside of the mechanical equipment. Chemical equipment is affected by acid, alkali, and oxygen, which directly causes corrosion of the mechanical equipment.
Chemical equipment is affected by multiple factors, but there are dominant corrosion points. Specific issues need to be analyzed in detail.