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Example: The condenser of a certain company, manufactured from naval brass, suffered rapid wear and corrosion damage due to the flow velocity at the inlet side exceeding 1.52 meters per second (the critical flow velocity). Later, condensers were made from Monel alloy. The critical flow velocity for Monel alloy is 2.1–2.4 meters per second; unfortunately, operators still control it according to the critical flow velocity of naval brass, resulting in pitting corrosion of the Monel alloy pipes. Analysis: This corrosion case shows that a lower flow rate is not necessarily better. For passive metal materials with a protective film formed on their surface, too low a flow rate can lead to liquid stagnation and deposition of solid substances, thereby causing pitting and crevice corrosion. For example, 304 stainless steel pumps are used for transporting seawater, and they are less prone to corrosion during operation. However, if the seawater-related equipment is not cleaned properly when the pump is not in use, pitting corrosion can occur quite quickly. Similarly, carbon steel equipment used for transporting 98% concentrated sulfuric acid also has this problem. The previous example showed that too high a flow rate causes corrosion damage, while too low a flow rate can lead to so-called \"gouge corrosion\", which results from the breakdown of the surface film on ferrous sulfate due to hydrogen evolution. An appropriate flow rate prevents hydrogen bubbles from accumulating on the metal surface, thus avoiding this type of corrosion. In summary, for equipment used to handle liquids, maintaining the flow rate within an appropriate range is a fundamental requirement for corrosion control. As for what the range of \"suitability\" is, different requirements apply to different materials.