• Crevice • Pitting • Intergranular • Weld Decay • Knife-Line Attack • Exfoliation • MIC • SCC • HB-HE-HIC • Fatigue • Stray Current • Index |
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Different Types of
Corrosion
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Intergranular Corrosion: Weld Decay |
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Recognition of Weld Decay |
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What is weld decay? Weld decay is a form of intergranular corrosion, usually of stainless steels or certain nickel-base alloys, that occurs as the result of sensitization in the heat-affected zone during the welding operation.
The corrosive attack is restricted to the heat affected zone (HAZ). Positive identification of this type of corrosion usually requires microstructure examination under a microscopy although sometimes it is possible to visually recognize weld decay if parallel lines are already formed in the heat affected zone along the weld (see photo below). |
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Mechanisms of Weld Decay |
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What causes weld decay? As in the case of intergranular corrosion, grain boundary precipitation, notably chromium carbides in stainless steels, is a well recognized and accepted mechanism of weld decay. In this case, the precipitation of chromium carbides is induced by the welding operation when the heat affected zone (HAZ) experiences a particular temperature range (550oC~850oC). The precipitation of chromium carbides consumed the alloying element - chromium from a narrow band along the grain boundary and this makes the zone anodic to the unaffected grains. The chromium depleted zone becomes the preferential path for corrosion attack or crack propagation if under tensile stress.
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Prevention of Weld Decay |
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How to prevent weld decay? Weld decay can be prevented through:
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For more details on Weld
Decay |
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Where can I learn more about
weld decay? More details on weld decay and
weldment corrosion are included in the following
corrosion courses which you can take as
in-house training courses,
course-on-demand, online
courses or distance
learning courses:
If you require corrosion expert witness or corrosion consulting service on weld decay, our NACE certified Corrosion Specialist is able to help. Contact us for a quote. |
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