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• Uniform • Galvanic • Crevice • Filiform • Pitting • Intergranular • MIC • SCC • HB-HE-HIC • Fatigue • Erosion • Stray Current • Index |
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Different Types of
Corrosion
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Crevice Corrosion |
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| Recognition |
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What is crevice corrosion? Crevice Corrosion refers to the localized attack on a metal surface
at, or immediately adjacent to, the gap or crevice between two joining
surfaces. The gap or crevice can be formed between two metals or a metal and
non-metallic material. Outside the gap or without the gap, both metals are
resistant to corrosion. The damage is normally confined to one metal at localized area within or close to the joining surfaces. In this photo, a 316 stainless steel tube and tube sheet from a heat exchanger in a desalination plant suffered crevice corrosion due to the presence of crevice (gap) between the tube and tube sheet. |
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| Mechanisms |
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What causes crevice corrosion? Crevice corrosion is initiated by a difference in concentration of some chemical constituents, usually oxygen, which set up an electrochemical concentration cell (differential aeration cell in the case of oxygen). Outside of the crevice (the cathode), the oxygen content and the pH are higher - but chlorides are lower. Chlorides concentrate inside the crevice (the anode), worsening the situation. The pH and the oxygen content are lower in the crevice than in the bulk water solution, just as they are inside a pit. Once a crevice has formed, the propagation mechanism for crevice corrosion is the same as for pitting corrosion. Ferrous ions form ferric chloride and attack the stainless steel rapidly. |
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| Prevention |
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How to prevent crevice corrosion? Crevice corrosion can be designed out of the system
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| For more details |
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More details on crevice corrosion are included in the following
corrosion courses which you can take as in-house training courses, online
courses or distance
learning courses:
Corrosion and Its Prevention (5-day module)
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