Stray current corrosion is a common threat to water-based steel structures such as barge terminals. Though hard to identify the source, damage from stray current can be prevented by following 3 simple steps.
A stray current refers to the existence of electrical potential between two objects that should not be subjected to an electric current, in this case, the steel structure and the water. This situation can arise from wiring flaws, an imbalanced electrical system, electrified railways, and grounded direct current sources. It is not always easy to find the source of stray electrical currents.
Common sources of stray currents:
The corroding process is known as electrolysis. Both cathodic, negative in this instance, and anodic, positive, currents work through the structure. However, the exit point where anodic currents transfer to the water are the areas on the structure that exhibit the most damage.
The rate at which a structure corrodes depends on its size, its conductivity, and the strength of the stray electrical current. A small structure that is subjected to a strong current is going to be more susceptible to damage than a larger structure subjected to a weak current. The time-frame in which evidence of damage appear could range from several years to as little as a few weeks.
The first step should be to try and identify the source of any stray current. Identifying the source of an electrical current is a difficult process, and we recommend hiring an experienced electrical contractor to check the condition of all wiring located on and near the water-based structures. This is as simple as inspecting wiring insulation, shore power connections, and proper grounding.
Since it is not always possible to find the source, the next solution is to redirect the current so that it no longer makes it to your dock structure. Redirecting the current may be as simple as installing a new grounding point located further away from the water. You may even consider using a metal that has better conductivity than iron-based steel, such as copper. We have used steel sheet pile wrapped in copper wire as a grounding point. Remember that electricity will always take the path of least resistance!
Stray current at barge terminals is common and very hard to identify until you observe pitting on the underwater portions of water-based steel structures. However, by taking three simple steps, you can prevent much of the damage that stray current creates. This will protect your investment, save you money, and ensure your structure will last for many years.