What does a shift of 30 mV over one hour in hull potential indicate during a corrosion survey?

A shift of 30 mV over one hour in hull potential during a corrosion survey indicates extreme under protection. In the context of corrosion protection systems, especially in marine environments, maintaining an appropriate hull potential is essential to prevent corrosion of the metal surfaces underwater.

The typical standard for a properly protected hull is to maintain a stable potential in a specific range that indicates the presence of effective cathodic protection. A shift or change in hull potential can reflect either the effectiveness or inadequacy of the corrosion protection in place. Specifically, a shift of 30 mV is significant and suggests that the protective measures are inadequate, leading to a higher likelihood of corrosion processes becoming active.

In cases of extreme under protection, the hull is essentially not receiving sufficient protective current, creating conditions ripe for corrosion. Monitoring these shifts over time is crucial for ensuring that corrosion protection systems are functioning correctly. Taking action to rectify the situation becomes essential to prevent substantial and costly damage to the hull from corrosion.