【Basic Knowledge 16】Characteristics of pitting and corrosion pits (prize quiz)
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What are the characteristics of pitting and corrosion pits respectively?
Pitting occurs when the diameter of the pit is smaller than the depth of the cavity. When the diameter of the pit opening is greater than the depth of the cave, it is called pit erosion.
A part of the metal is corroded to form small, deep pitting; as the corrosion products and the medium become more concentrated at the bottom of these pits, their effect intensifies, causing the pits to become deeper, and in some cases perforation even occurs. Pitting corrosion, also known as spot corrosion or pit corrosion, is a type of corrosion that occurs in specific areas and progresses inward into the metal, forming pits or holes. When the pit diameter is smaller than the cave depth, it is called pitting corrosion. If the diameter of the pit opening is greater than the depth of the pit, it is called pit erosion
What are the characteristics of pitting and corrosion pits respectively? Pitting occurs when the diameter of the pit is smaller than the depth of the cavity. When the diameter of the pit opening is greater than the depth of the cave, it is called pit erosion.
Rust formation occurs in extremely localized areas on the metal surface. It causes cavities or pits that expand inward, and can even lead to perforations. When the pit diameter is smaller than the cave depth, it is called pitting corrosion. If the diameter of the pit opening is greater than the depth of the pit, it is called pit erosion. In fact, there is no strict boundary between pitting and cratering.
Rust formation occurs in extremely localized areas on the metal surface. It causes cavities or pits that expand inward, and can even lead to perforations. When the pit diameter is smaller than the cave depth, it is called pitting corrosion. If the diameter of the pit opening is greater than the depth of the pit, it is called pit erosion. In fact, there is no strict boundary between pitting and cratering.
Corrosion occurs in very localized areas on the metal surface, forming cavities or pits that expand inward and can even lead to perforations. When the diameter of the pit opening is smaller than the depth of the cavity, it is called pitting corrosion; if the diameter of the pit opening is larger than the depth of the pit, it is called crevice corrosion
Rust formation occurs in extremely localized areas on the metal surface. It causes cavities or pits that expand inward, and can even lead to perforations. When the pit diameter is smaller than the cave depth, it is called pitting corrosion. If the diameter of the pit opening is greater than the depth of the pit, it is called pit erosion. In fact, there is no strict boundary between pitting and cratering.
The failure phenomenon of materials, mechanical parts, or components resulting from the combined action of static stress (mainly tensile stress) and corrosion. It often occurs in boiler steel, brass, high-strength aluminum alloys, and stainless steel. Stress corrosion is also significant in components such as condenser tubes, steel cables used in mining, and the inner walls of high-pressure cylinders used for aircraft emergency braking. The mechanism of common stress corrosion is as follows: under the combined action of stress and a corrosive environment, the oxide film on the surface of a part or component is corroded and damaged. The damaged surface and the undamaged surface act as the anode and cathode respectively; the metal at the anode is dissolved into ions, generating an electric current that flows toward the cathode. Since the anode area is much smaller than that of the cathode, the current density at the anode is high, further corroding the already damaged surface. With the effect of tensile stress, cracks gradually form at the failure site, and these cracks expand over time until fracture occurs. Such cracks can develop not only along the grain boundaries of the metal but also through the grains. Experimental studies on the stress corrosion process show that applying an anodic current to a metal can exacerbate stress corrosion, whereas applying a cathodic current can stop it. It is generally believed that compressive stress has little effect on stress corrosion.
Erosion occurs in extremely localized areas on the metal surface, creating cavities or pits that expand inward and may even lead to perforations. When the diameter of the pit opening is smaller than the depth of the cavity, it is called pitting corrosion; if the diameter of the pit opening is larger than the depth of the pit, it is called crevice corrosion
Pitting occurs when the diameter of the pit is smaller than the depth of the cavity. When the diameter of the pit opening is greater than the depth of the cave, it is called pit erosion.