Discuss cavitation corrosion and improvement measures
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Cavitation corrosion, abbreviated as cavitation or aerocavitation, is a special form of wear corrosion. The presence of bubbles in the high-speed fluid causes severe wear and corrosion. The formation of cavities is caused by local pressure drops resulting from liquid turbulence or temperature changes. These cavities contain only a small amount of water vapor and exist for a very short period of time. When they collapse, the resulting shock wave pressure can reach up to 4,000 atm, which destroys the protective metal film and can induce plastic deformation or even tear apart metal particles. The bare metal at the membrane rupture site corrodes, followed by the regrowth of a membrane. New bubbles form at the same spot and then burst quickly; this process repeats itself, resulting in dense and deep pores on the metal surface, giving it a very rough appearance. Cavitation often occurs in pump impellers, hydraulic turbines, etc. To prevent cavitation, the design can be improved to reduce the dynamic pressure difference of the fluid in the flow; alternatively, materials more resistant to cavitation or surfaces with a high degree of finish can be used, as smooth surfaces do not provide nuclei for bubble formation. Using a flexible protective layer (plastic or rubber) or cathodic protection is also effective.
Cavitation corrosion is a phenomenon in which, due to pressure changes during fluid flow, bubbles form locally; the collapse of these bubbles generates high-pressure shock waves that destroy the protective layer on the metal surface, leading to severe corrosion and damage. To prevent cavitation erosion, measures such as improving the design to reduce fluid dynamic pressure differences, selecting cavitation-resistant materials, finely polishing surfaces to minimize cavitation nuclei, or applying elastic protective coatings and cathodic protection can be taken to mitigate or prevent its occurrence. .
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