Intergranular Corrosion via Chromium Depletion
Intergranular corrosion due to chromium depletion occurs at grain boundaries due to chromium-rich carbide precipitates and matrix-near chromium depletion. This leads to local corrosion and cracking.
Physical-chemical mechanism of action
Chromium-rich carbides, such as cobalt hydrocarbon (Cr₃C₂), form during the welding process. These carbides have high solubility in the matrix and lead to chromium depletion at grain boundaries. The remaining chromium reaction near the matrix then forms a protective layer, which leads to local corrosion at the unprotected grain boundaries.
Metallurgical relevance & risks during welding
This corrosion can lead to local cracks and deformation of the weld. It is particularly dangerous because it is not immediately visible and affects the mechanical properties of the weld. This reduces the service life of the component.
Workshop practice & instructions
To avoid intergranular corrosion due to chromium depletion, it is important to ensure correct welding parameter selection and execution. This includes:
• An optimal melt time of 15 to 20 seconds
• A cooling time of 30 to 40 seconds after welding
• The use of stabilized steels with low chromium content
• Proper pre-treatment of the workpiece to minimize carbide formation.