【Basic Knowledge 20】What is crevice corrosion? (Premium quiz)
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This post was last edited by lzy4225925 on 2015-12-21 09:17. What is crevice corrosion? Local corrosion occurs in gaps and concealed areas due to the accumulation of a small amount of stagnant solution; this often happens in holes, the undersides of gaskets, as well as in the gaps beneath joints, screws, and rivet heads ； Typically, the slit width is 0.1 mm
Many metal components are connected by screws, rivets, or welding; defects in these connecting elements or welding joints can result in narrow gaps (0.025–0.1 mm) that are large enough for electrolyte to enter. This allows the metal inside the gap to form a short-circuited galvanic cell with the metal outside the gap, leading to severe corrosion. This type of local corrosion is known as crevice corrosion.
Crevice corrosion refers to the formation of spot-like or ulcerated macroscopic corrosion pits at the gaps in metal components; it is a type of localized corrosion that often occurs at joints such as gaskets, rivets, and screws, as well as in overlapping welded joints, valve seats, and between stacked metal sheets. The mechanism of crevice corrosion arises from the fact that consecutive crevices are covered by corrosion products, and the diffusion of the medium is restricted; as a result, the composition and concentration of the medium in those areas differ significantly from those in the overall area, leading to \"closed-circuit cell corrosion\".
In a medium, metal suffers from severe localized corrosion in areas with gaps or on surfaces covered by other substances; this type of corrosion is known as crevice corrosion. In addition to being caused by differences in metal ion concentrations or dissolved oxygen levels within the gap compared to those around it, the main reason for crevice corrosion is the autocatalytic process associated with this type of corrosion; the hydrolysis of metal chlorides in the gap leads to a rapid decrease in pH, thereby accelerating the dissolution of the metal.
Crevice corrosion refers to the formation of spot-like or ulcerated macroscopic corrosion pits at the gaps in metal components; it is a type of localized corrosion that often occurs at joints such as gaskets, rivets, and screws, as well as in overlapping welded joints, valve seats, and between stacked metal sheets.
Many metal components are connected using screws, rivets, welding, and other methods. Narrow gaps can form at defects in these connections or weld joints; the width of such gaps (usually between 0.025 and 0.1 mm) is sufficient for electrolyte solutions to enter. This allows the metal inside the gap to form a short-circuited galvanic cell with the metal outside the gap, leading to severe corrosion within the gap. This type of localized corrosion is known as crevice corrosion.
Many metal components are connected using screws, rivets, welding, and other methods. Narrow gaps can form at defects in these connections or weld joints; the width of such gaps (usually between 0.025 and 0.1 mm) is sufficient for electrolyte solutions to enter. This allows the metal inside the gap to form a short-circuited galvanic cell with the metal outside the gap, leading to severe corrosion within that gap. This type of localized corrosion is known as crevice corrosion
Many metal components are connected using screws, rivets, welding, and other methods. Narrow gaps can form at defects in these connections or weld joints; the width of such gaps (usually between 0.025 and 0.1 mm) is sufficient for electrolyte solutions to enter. This allows the metal inside the gap to form a short-circuited galvanic cell with the metal outside the gap, leading to severe corrosion within the gap. This type of localized corrosion is known as crevice corrosion.
Typically, the oxygen concentration difference between the inside and outside of the gap causes potential difference electrochemical corrosion
Many metal components are connected using screws, rivets, welding, and other methods. Narrow gaps can form at defects in these connections or weld joints; the width of such gaps (usually between 0.025 and 0.1 mm) is sufficient for electrolyte solutions to enter. This allows the metal inside the gap to form a short-circuited galvanic cell with the metal outside the gap, leading to severe corrosion within the gap. This type of localized corrosion is known as crevice corrosion.