PR405-173610-R01 Develop New Criteria for DC Stray Current Interference

This report refers to the activities performed in the frame of PRCI project on the refinement of the dynamic DC stray current corrosion criteria by applying an advanced DC corrosion prediction model.

In order to find realistic stray current interference conditions, an industry survey was performed to retrieve dynamic DC interference signals on real-world pipelines. After analysis of the cases, a simulation matrix was proposed that covers a wide variety of interference conditions. The simulated signals were simplified as squared pulses.

The European Standard EN 50162 Protection against corrosion stray current from direct current systems was used a reference for validation. Some other criteria that are currently under investigation have been considered as well. The criteria were validated against simulated corrosion rates.

The final goal is achieving a further refinement of the dynamic DC stray current criteria. The simulations demonstrate that current criteria are either not valid, either too conservative when steel tends to passivate under anodic excursions in high pH soil due to the development of a Fe3O4 film. The lowest pH value at which the passive film developed was 10.34 with relatively short cathodic duration (30 sec) and long (50 sec) and strong (-200 mVcse) anodic potential.