Corrosion cheat sheet

Corrosion problems with 300 series stainless steel 19-05 

Types of Corrosion with 300 series stainless steel

  • Chloride Stress corrosion.
    • Four things necessary. The exact percentage of each is unknown
      • The presence of chlorides (There are more chlorides in this world than any other chemical)
      • 300 series stainless steel. (The most popular)
      • Corrosion slows down below 40В°F (5В°C) and above 285В°F (140В°C.)
      • Tensile stress.
    • What happens?
      • Forms Cr2O3 on metal surface. This is called pacification,
  • Concentrated cell or crevice corrosion
    • Salt water is low in Ph (8.0 to 9.0) and high in chlorides
  • Erosion/ corrosion
    • Fluid movement removes the protective oxide layer exposing the softer stainless steel.
  • Fretting corrosion
    • Rubbing removes the protective oxide layer
  • Galvanic corrosion
  • General corrosion
    • Doubles each 10В°C (20В°F )rise in temperature
  • Intergranular
    • At 1050В°F (565В°C) to 1600В° F(870В°C) Carbon in steel combines with the chrome to form chrome carbide.
    • This is a normal welding temperature.
    • Fix
      • Anneal the piece after welding to remove stress.
      • Use low carbon type stainless steel.
      • Add columbium to form columbium carbide. Metal is said to be stabilized.
  • Micro organisms
    • Aerobic, the kind that need oxygen.
    • Anaerobic, the kind that do not need oxygen.
    • Facultative, the type that goes both ways. They operate with or without oxygen
  • Pitting
  • Selective leaching
  • Zinc embrittlement

Posted

  • On February 13, 2018