Rat Tailing or Oxidation Crazing

Rat Tailing or Oxidation CrazingRat tailing or oxidation crazing presents as river-like depressions, mostly linear grooves, in the casting. This defect indicates that the primary coats cracked slightly, giving access to oxygen. The reaction between oxygen and the metal follows a crack in the shell.

The causes of this defect are evident in the shell and other portions of the process. To cure these causes, R&R recommends taking the following actions.








  1. See shell causes for finning.
  2. Drying stresses.
  3. Low quality primary binder or poor slurry control.
  1. See shell cures for finning.
  2. Use a high quality primary binder.
  3. Avoid very low refractory loadings and control the slurry.





  1. Oxygen reaction with metal.
  2. Chromium (Cr) oxides form when oxygen is present during solidification.
  3. CO gas forms through reaction between C in steel with the refractories of the mold.
  1. Eliminate/reduce oxygen presence after pouring.
  2. Avoid contact with oxygen during solidification. Implement canning practice once shells are poured.
  3. Use carbon stucco, put molds in sand and use alternative refractories.

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