Stress Corrosion Cracking of CS & SS

[Nabeel Ahmed Qureshi]

I've heard about SCC in Stainless steels but can any body comment on SCC of Carbon steels? What are the particular conditions (Service, temperature etc ) at which this phenomena can occur. Also how this can be prevented?

[ashfaqanwer]

Phenomenon of SCC occurs when certain combinations of metal and environment are formed. And yes in Carbon Steels, SCC do occur in following environments:

Environment (failure mode)
1. Aerated water with temperature > 200 deg C (trans-granular cracking - across the grain boundaries)
2. Liquid ammonia with low temperature (same as 1)
3. Hydroxides in high concentrations and near boiling temperatures (Inter-granular cracking - along the grain boundaries)
4. Nitrates in moderate concentrations at temperature < 100 deg C (same as 3)
5. Carbonates / Bicarbonates in lower concentrations at temperature < 100 deg C (same as 3)
6. Carbon dioxide / water at temperature < 100 deg C (same as 1)

To prevent, avoid the combination of these environments and Carbon Steel. Choose the right material not susceptible to SCC for the specific environment or otherwise, control the environment.

Hope this would help.