DC Stray Current Corrosion

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What is DC Stray Current Corrosion, and can it impact a structure with a cathodic protection system? Learn more about when a structure might be affected by stray current and some mitigation techniques to protect it.

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Stray current refers to current that flows somewhere other than the intended current path.
When this stray current flows through a pipeline or other metal structure, it can cause corrosion.

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Major DC Stray Current sources include power distribution lines, railway systems, substations, mining operations and welding operations.  These sources all generate DC stray currents that can corrode nearby structures.

Even the Impressed Current Cathodic Protection (ICCP) systems protecting other metal structures can cause stray current corrosion in nearby structures.

Scene #3:

Electrical currents follow the path of least resistance to complete a circuit.
Because pipelines and other metal structures are highly conductive, stray current from an external source can travel through them to complete the circuit.

Corrosion appears at the point where the current exits the structure to return to its origin.

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Before you can attempt to eliminate the problem, you will need to determine several things:

  • The source of the DC stray current affecting your structure
  • The point where the current exits your structure
  • The voltage and amount of current at the exit point

Some of the tools you will need to help you detect and analyze the scope of the stray current and the affected area are:

  • Interrupter - Model TriStar
  • Survey Equipment- American Innovations Allegro QX
  • Data Logger DL-1

Scene #5:

Every source of DC stray current has its own characteristics. For example, the stray current generated by a DC railway system may be low most of the time, but spike whenever a train accelerates out of a nearby station.

You will need to monitor the source for a period of time to understand its unique characteristics and assess the risk to your structure.

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Some potential mitigation techniques include:

  • Applying additional cathodic protection at the point where the current exits your structure
  • Adding sacrificial anode to both structures
  • Improving insulation at the source of the stray current
  • Increasing the distance between your structure and the interfering structure
  • Install an electrical resistance bond between the two structures to return the stray current safely

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About Allied Corrosion

Allied Corrosion Industries, Inc. is a full service corrosion control corporation providing design, installation and maintenance of corrosion solutions and cathodic protection systems since 1980. We are also a materials and test equipment provider, offering a full line of corrosion-related products.

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