In the chemical industry, pressure vessels such as distillation columns must satisfy special requirements regarding safety and availability. Given this, they are made from high-strength materials such as duplex stainless steels. Such steels include both austenitic and ferritic phases and, therefore, have long been considered resistant to stress corrosion cracking.
Figure 1. After corrosion problems, column was rebuilt using duplex stainless steel but stress corrosion cracking occurred after a few years.
Figure 2. The inside surface of the column’s duplex-stainless-steel bottom exhibited pits after five years in service.
Figure 3. The weld seam at the bottom of the column also showed significant signs of attack.
Figure 4. Some fissures in the austenitic phase (bright; ferritic phase, dark) extended right through the column wall.