The principle of metal corrosion: Metal corrosion refers to the destruction of metal under the action of chemical or electrochemical surrounding media, and often under the joint action of physical, mechanical or biological factors, that is, the metal in its environment The damage caused by the effect.
Several common types of corrosion damage of heat exchangers:
1. Uniform corrosion, which occurs on the entire surface exposed to the medium or on a larger area. Macroscopically uniform corrosion damage is called uniform corrosion.
2. Contact corrosion. Two metals or alloys with different potentials are in contact with each other and immersed in the electrolyte solution. When there is current between them, the corrosion rate of metals with positive potential decreases and the corrosion rate of metals with negative potential increases.
3. Selective corrosion. The phenomenon that a certain element in the alloy preferentially enters the medium due to corrosion is called selective corrosion.
4. The pitting corrosion is concentrated on the individual small spots on the metal surface. The deeper corrosion is called pitting corrosion, or small hole corrosion, pitting corrosion.
5. Crevice corrosion, there will be severe crevice corrosion in the crevices and covered parts of the metal surface.
6. Scour corrosion, scour corrosion is a kind of corrosion that accelerates the corrosion process due to the relative movement between the medium and the metal surface.
7. Intergranular corrosion. Intergranular corrosion is a kind of corrosion that preferentially corrodes the grain boundaries of metals or alloys and the areas near the grain boundaries.
8. Stress corrosion cracking (SCC) and corrosion fatigue SCC is a material fracture caused by the combined action of corrosion and tensile stress in a certain metal-medium system.
9. Hydrogen destruction. Metals in electrolyte solutions can be damaged due to hydrogen penetration due to corrosion, pickling, cathodic protection or electroplating.
没有评论:
发表评论