Learn about the corrosion principles of valves
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This post was last edited by Wang Wei2 on 2025-6-4 11:17. The corrosion of metals is mainly caused by chemical corrosion and pitting corrosion, while the corrosion of non-metallic materials is generally resulting from direct chemical and physical actions. 1. Chemical corrosion: The surrounding medium reacts chemically with the metal directly, without the generation of an electric current, thereby causing damage to the metal; examples include the corrosion of metals by high-temperature dry gases and non-electrolytic solutions. 2. Electrochemical corrosion: When a metal comes into contact with an electrolyte, electron flow occurs, leading to the degradation of the metal as a result of electrochemical reactions; this is the main form of corrosion. Common types of corrosion such as corrosion caused by acids, bases, and salts, atmospheric corrosion, soil corrosion, seawater corrosion, microbial corrosion, pitting corrosion, and crevice corrosion in stainless steel are all forms of electrochemical corrosion. Electrochemical corrosion occurs not only between two substances that can undergo chemical reactions, but also due to differences in solution concentration, differences in the concentration of oxygen around them, and minor differences in the structure of the substances, which create potential differences and thus provide the driving force for corrosion, resulting in damage to the metal with the lower potential, which is in the anode position.
The corrosion mechanism of valves is the same as that of metallic and non-metallic materials, and it mainly includes: 1. Chemical corrosion: The environmental medium in which the valve is located undergoes a chemical reaction directly with the metal surface of the valve in the absence of electrical current, resulting in oxidation, dissolution of the metal surface, or the formation of other compounds, thereby causing damage to the material. This type of corrosion often occurs in high-temperature dry gases and non-electrolytic liquids. 2. Electrochemical corrosion: When the metal of a valve comes into contact with an electrolyte that has electrical conductivity (such as acids, bases, or saltwater), a potential difference causes electrons to flow, forming a corrosion cell that leads to the anodic dissolution and damage of the metal. This form is more common; corrosion caused by acid-base-salt solutions, seawater corrosion, atmospheric corrosion, pitting and crevice corrosion of stainless steel all fall under electrochemical corrosion. The driving forces behind electrochemical corrosion stem mainly from the contact between two different metals (such as dissimilar metal joints), differences in the oxygen or ion concentration of the medium, and irregularities in the material’s microstructure. In practical applications, corrosion protection for valves requires taking into full account the type of corrosive medium and the operating conditions; accordingly, corrosion-resistant materials should be selected, protective coating treatments applied, or cathodic protection measures implemented. .