Super duplex pitting potential
Super duplex pitting potential is the current density-potential threshold above which the oxide film on super duplex steels breaks down in chloride-rich environments, initiating pitting corrosion.
Physical-Chemical Mechanism of Action
Superduplex steels contain high amounts of chromium and nickel, which protect them against corrosion. However, in chloride-rich environments, the oxide layer can be breached under certain electrical conditions. The superduplex pitting potential indicates the current density-potential threshold above which this oxide layer is locally broken down and pitting corrosion sets in.
Metallurgical Relevance & Welding Risks
If the superduplex pitting potential is exceeded, the oxide layer can be broken down in the weld seam areas. This leads to pitting corrosion and reduces the service life of the components. There is also a risk of hot cracking and distortion if cooling is insufficient.
Workshop Practice & Instructions
To minimize the superduplex pitting potential, the following measures should be taken:
• Use correct welding process parameters (target temperature, cooling time).
• Ensure the environment is free of chloride ions or that the components are properly cleaned and treated after welding.
• Monitor the susceptibility to electrolytic corrosion through periodic inspections.