Understanding Stray Current Interference

1. Sources of Stray Current

• DC interference may arise from external cathodic protection systems, DC-powered transmission lines, mining equipment, or voltage imbalances in high-voltage DC transmission applications.
• AC interference is typically caused by nearby high-voltage power lines or grounding networks, which create electromagnetic coupling with pipelines.

2. Types of Stray Current and Their Effects

• DC Interference
• Leads to unwanted polarization; areas where current discharges from the structure experience accelerated corrosion.
• Commonly appears as localized pitting, especially at coating defects, and over time can significantly reduce pipeline wall thickness.
• AC Interference
• Induced AC current reduces cathodic protection effectiveness, disrupts polarization, and causes localized corrosion.
• In addition to corrosion, high induced AC voltages (>15 VAC) pose serious safety hazards, including the risk of electric shock.

3. Effective Mitigation Strategies

• For DC Interference
• Conduct close-interval surveys (CIS) and ON/OFF potential measurements to identify affected areas.
• Apply mitigation methods such as direct or resistive bonds, recoating, dielectric shielding, or drain anodes to safely divert stray currents away from pipelines.
• Install sacrificial anodes or bonding points at interference locations to transfer current without damaging the pipeline metal.
• For AC Interference
• Monitor AC current density:
• When DC current density is >1 A/m², keep AC density below 30 A/m².
• When DC current density is <1 A/m², AC density may be up to 100 A/m².
• Electrically isolate pipelines using monolithic isolation joints or insulating flange kits.
• Use gradient control mats, zinc ribbon grounding, or decouplers to reduce AC coupling and ensure pipeline safety.
• Perform remote monitoring every 24–48 hours to detect fluctuations linked to AC load cycles.

Why Our Integrated Solutions Matter

At our factory, we provide end-to-end cathodic protection solutions:

• Project design by NACE-certified experts, including:
• Tailored SACP systems with high/low potential magnesium anodes.
• ICCP systems featuring MMO ribbon, flexible, or tubular anodes.
• High-quality accessories, including cables, test stations, and isolation fittings.

All of our materials are engineered to ensure optimal system performance, safety, and service life—empowering asset owners to protect pipelines with confidence.