19-05 Corrosion problems with 300 series stainless steel
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 40°F (5°C) and above 285°F (140°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
- Doubles each 10°C (20°F )rise in temperature
- At 1050°F (565°C) to 1600° F(870°C) Carbon in steel combines with the chrome to form chrome carbide.
- This is a normal welding temperature.
- 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
- Selective leaching
- Zinc embrittlement
about my CD with over 600 Seal & Pump Subjects
Link to Mc Nally home page www.mcnallyinstitute.com