We cannot guarantee that the pump will not be corroded and will only reduce its corrosion. So what are the corrosion of the pump? How to prevent it?
(1) Wear corrosion: A kind of corrosion of a metal surface by a high-speed fluid. Pumps wear out during operation, so we should use materials with good wear resistance to reduce wear and corrosion. Of course, the wear resistance of different materials is also different.
(2) Electrochemical Corrosion: An electrochemical process in which the contact surface of the dissimilar metal forms a battery due to the difference in potential between the electrodes, thereby causing corrosion of the anode metal. Measures to prevent electrochemical corrosion are: 1.using a sacrificial anode to protect the cathode metal; 2. the pump's flow path is preferably made of the same metal material.
(3) Intergranular corrosion: Intergranular corrosion is a kind of local corrosion, which mainly refers to the phenomenon of precipitation of chromium carbide between stainless steel grains. Intergranular corrosion is extremely corrosive to stainless steel materials. Measures to prevent intergranular corrosion are: annealing stainless steel or ultra-low carbon stainless steel (C < 0.03%).
(4) Uniform corrosion: When the corrosive liquid contacts the metal surface, uniform chemical corrosion occurs on the entire metal surface.This is the most common type of corrosion type and the least hazardous type of corrosion. The measure to prevent uniform corrosion is to use suitable materials (including non-metals).
(5) Crevice corrosion: Crevice corrosion is a type of local corrosion. After the gap is filled with corrosive liquid, corrosion is caused by local destruction of the metal passive film due to a decrease in oxygen content in the gap and a decrease in pH. The use of metals with high Cr and M0 content prevents or reduces crevice corrosion.
(6) Pitting corrosion: Pitting corrosion is a type of local corrosion. because a localized destruction of the metal passive film causes a certain partial area of the metal surface to rapidly form a hemispherical pit. Pitting corrosion is mainly caused by Cl. To prevent pitting corrosion,M0-containing steel (usually 2.5% Mo) can be used. And as the Cl content and temperature increase, the M0 content should also increase accordingly.
(7) Stress corrosion: A type of local corrosion caused by the combination of stress and corrosive environment. The measure to prevent stress corrosion is to use austenitic Cr-Ni steel with a high Ni content (Ni; >25%to 30%).
(8) Cavitation corrosion: Corrosion caused by cavitation of the pump is called cavitation corrosion. The most practical and convenient way to prevent cavitation corrosion is to prevent cavitation. However, pump cavitation can't stop it, and the pump will generate cavitation more or less.For those pumps that often generate cavitation corrosion, cavitation resistant materials can be used to increase their cavitation resistance.
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