Caustic soda (sodium hydroxide) is one of the most widely used inorganic chemicals in water treatment process. Improper injection rate or concentration have led to many failures in the industry. These failures have been mostly identified as Caustic Stress Corrosion Cracking (CSCC).
Caustic Stress Corrosion Cracking (CSCC) is a form of Environment Assisted Cracking (EAC), characterized by surface-initiated cracks that occur in materials exposed to caustic environment. EAC is defined as a cracking process caused by the synergistic effects of stress, and environment on a specific material. All three factors–stress, aggressive environment, and susceptible material are necessary for EAC. The environment aggressiveness escalates with increase of caustic concentration and metal temperature, in case of CSCC.