No matter what kind of centrifugal pump, corrosion will occur during use? If stainless steel pump, fluorine plastic pump, ordinary cast iron pump. Our Bulletproof Pump Industry cannot guarantee 100% that the pump will not be corroded, but can only reduce its corrosion. So what kind of corrosion does the water pump have? How to prevent it?
Methods to prevent corrosion of water pump:
1) Wear and corrosion
Refers to the erosion and corrosion of metal surfaces by high-speed fluids. Fluid erosion erosion is different from the erosion caused by solid particles in the medium. Water pumps will wear out during operation, so we must try our best to use materials with good wear resistance to reduce wear and corrosion. Of course, different materials have different wear and corrosion resistance.
2) Electrochemical corrosion
Electrochemical corrosion refers to the electrochemical process in which the contact surface of dissimilar metals forms a battery due to the difference in electrode potential between metals, thereby causing the anode metal to corrode. To prevent electrochemical corrosion, one is to use a sacrificial anode to protect the cathode metal; the other is to use the same metal material for the flow channel of the pump.
3) Intergranular corrosion
Intergranular corrosion is a kind of localized corrosion, mainly refers to the phenomenon of chromium carbide precipitation between stainless steel grains. Intergranular corrosion is extremely corrosive to stainless steel materials. The measures to prevent intergranular corrosion are: annealing the stainless steel or using ultra-low carbon stainless steel (C<0.03%).
4) Uniform corrosion
Uniform corrosion refers to the uniform chemical corrosion of the entire metal surface when corrosive liquid contacts the metal surface. This is the most common type of corrosion type and also the least harmful type of corrosion type. The measures to prevent uniform corrosion are: adopt suitable materials (including non-metals), and consider sufficient corrosion margin when designing the pump.
5) Crevice corrosion
Crevice corrosion is a kind of local corrosion, which refers to the corrosion caused by the partial destruction of the metal passive film due to the decrease of oxygen content in the crevice and/or the decrease of pH value after the crevice is filled with corrosive liquid. The use of metals with high Cr and M0 content can prevent or reduce the occurrence of crevice corrosion.
6) Pitting corrosion
Pitting corrosion is a localized corrosion. The partial destruction of the metal passive film causes the rapid formation of hemispherical pits in a local area of the metal surface. This phenomenon is called pitting corrosion. Pitting corrosion is mainly caused by Cl-. To prevent pitting corrosion, steel containing M0 (usually 2.5% Mo) can be used, and as the Cl content and temperature rise, the M0 content should also increase accordingly.
7) Stress corrosion
Stress corrosion refers to a kind of local corrosion caused by the joint action of stress and corrosion environment. The measure to prevent stress corrosion is to use austenitic Cr-Ni steel with high Ni content (Ni; >25%-30%).
8) Cavitation corrosion
The corrosion caused when the pump cavitation occurs is called cavitation corrosion. The most practical and simple way to prevent cavitation corrosion is to prevent cavitation. However, cavitation of water pumps cannot be prevented. Cavitation will occur more or less during operation. For those pumps that often produce cavitation corrosion, cavitation-resistant materials can be used to increase their cavitation resistance.
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