• Crevice • Pitting • Intergranular • Weld Decay • Knife-Line Attack • Exfoliation • MIC • SCC • HB-HE-HIC • Fatigue • Index

Different Types of Corrosion
- Recognition, Mechanisms & Prevention

Intergranular Corrosion: Knife-Line Attack (KLA)

Recognition

What is knife-line attack? Knife-Line Attack (KLA) is a form of intergranular corrosion of an alloy, usually stabilized stainless steel, along a line adjoining or in contact with a weld after heating into the sensitization temperature range.

The corrosive attack is restricted to extremely narrow line adjoining the fusion line. Attack appears razor-sharp (and hence the name of "knife-line" attack). It is possible to visually recognize knife-line attack if the lines are already formed in the along the weld.

What causes knife-line attack? For stabilized stainless steels and alloys, carbon is bonded with stabilizers (Ti or Nb) and no weld decay occurs in the heat affected zone during welding. In the event of a subsequent heat treatment or welding, however, precipitation of chromium carbide is possible and this leaves the narrow band adjacent to the fusion line susceptible to intergranular corrosion.

• Heat treatment - heating the weld to 1065^oC to re-stabilize the material.

Corrosion and Its Prevention (5-day module)
Corrosion and Its Prevention (2-day module)
Corrosion, Metallurgy, Failure Analysis and Prevention (3 days)
Marine Corrosion, Causes and Prevention (2 days)
Materials Selection and Corrosion (2 days)
Stainless Steels and Alloys: Why They Resist Corrosion and How They Fail (2 days)

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