Discuss impact corrosion in wear and corrosion and its solutions

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When a metal surface is subjected to high-flow-rate and turbulent fluids, it suffers both wear and corrosion damage, a condition known as wear corrosion. Impact corrosion is the main form of wear corrosion. Under the impact of high-speed fluids, the protective film on the metal is damaged, causing the exposed metal at the fracture site to corrode more rapidly. If the fluid contains solid particles, wear and corrosion become more severe. Its external features include localized grooves, ripples, circular holes, and valley shapes, which usually exhibit directionality. Devices exposed to moving fluids, such as pipes, tees, valves, blowers, centrifuges, impellers, heat exchangers, exhaust ducts, etc., can all suffer from impact corrosion. Soft metals such as copper and lead are even more severe. Impact corrosion occurs most frequently at the points where the fluid changes direction. Such as elbows, tees, cyclones, and the areas opposite to the containers and inlet pipes. At the inlet of the condenser and heat exchanger tube bundles, the fluid flows from a larger cross-section into a smaller one, resulting in turbulence; severe corrosion often occurs within a few dozen millimeters of the tube inlet. To prevent impact corrosion, materials with better wear resistance can be used; for example, alloy 20 is superior to 18/8 stainless steel, and 90Cu/10Ni is better than 70Cu/30Ni in seawater. Design improvements, changes to the environment, or the use of coatings and cathodic protection can also help.