Galvanic isolation: Protection of assets against parasitic currents

Galvanic isolation represents a fundamental tool for protecting industrial assets exposed to unwanted electrical phenomena. In facilities where cathodic protection systems, power electrical networks, substations, variable frequency drives, and buried metallic structures coexist, the presence of stray currents can pose a significant risk to structural integrity. Understanding how galvanic isolation works and how it integrates into a stray current corrosion control strategy is essential to ensure operational reliability and infrastructure sustainability.

What is galvanic isolation?

Galvanic isolation is a design technique that electrically separates two circuits in order to prevent the direct transfer of unwanted direct or alternating current between them. Although energy or signals may be transmitted through magnetic, capacitive, or optical coupling, there is no direct electrical continuity. As described by Wikipedia and in the technical documentation of Riello UPS, this principle allows the blocking of ground potential differences, induced currents, and electrical interference phenomena, protecting both equipment and personnel.

In the industrial field, the concept goes beyond electronics and acquires a structural dimension. Galvanic isolation applied to pipelines, tanks, and buried systems allows control of current paths that could otherwise become active electrochemical cells, generating accelerated corrosion at specific locations.

Stray currents and stray current corrosion

Stray currents are electrical flows that circulate through paths different from those originally intended in a system design. When these currents enter a buried metallic structure and subsequently discharge into the soil, a localized electrochemical process known as stray current corrosion is generated. Unlike traditional galvanic corrosion, this phenomenon does not depend exclusively on the potential difference between dissimilar metals, but rather on the presence of an external current that creates anodic zones at the discharge point.

This type of corrosion is particularly critical because it manifests only at the point where the current leaves the metal and enters the electrolyte, generating accelerated material loss. It can affect transmission pipelines, storage tanks, electrified railway structures, and any buried metallic asset located near direct current sources.

Among the most common causes are unbalanced cathodic protection systems, grounded direct currents, poorly distributed substations, electric transit systems, and welding equipment. Even a system designed to protect against corrosion may, if not properly controlled, become a source of electrical interference or DC interference.

How does galvanic isolation work in plant?

In plant environments, galvanic isolation acts as a strategic barrier that interrupts electrical continuity without affecting mechanical or hydraulic continuity. This means that fluid can circulate normally through a pipeline, but electrical current cannot pass through certain critical points of the system.

This separation is achieved through devices such as insulating flanges, isolation joints, or so-called monolithic isolation joints. An insulating flange kit may also be used when a modular solution including gaskets, insulated bolts, and dielectric washers is required. In auxiliary electrical systems, the isolation transformer performs a complementary function by transferring energy without direct galvanic connection between circuits.

When properly installed, galvanic isolation prevents a potential difference in one section of the plant from propagating to another, reducing the possibility of forming unwanted current paths. This electrical segmentation makes it possible to delimit cathodic protection zones and minimize interaction between nearby assets.

Stray current mitigation and isolation

Effective stray current mitigation requires a comprehensive approach. It is not sufficient to install insulating devices; it is necessary to understand the electrical behavior of the entire system. Structure-to-soil potential measurements, voltage gradient analysis, and leakage current mapping allow identification of points where current enters and leaves the structure.

Once the paths are identified, galvanic isolation can be strategically used to interrupt the unwanted electrical circuit. In this context, coordination with the cathodic protection design is essential. Excessive protection may generate interference in neighboring structures, while insufficient protection will not adequately mitigate the corrosive process.

Isolation also plays an important role during transient events such as overvoltage, lightning, or AC fault. Atmospheric discharges or alternating current faults may induce significant potential differences which, if not controlled, could damage components or compromise structural integrity.

How to reduce stray current corrosion?

Reducing stray current corrosion involves acting both on the current source and on the vulnerability of the asset. The first step is to evaluate the quality of grounding systems and the proper installation of electrical systems. Subsequently, the performance of the cathodic protection system must be verified and the applied current levels adjusted.

Installing isolation joints at strategic points prevents external currents from traveling along long pipeline sections. Likewise, the use of isolation transformers in sensitive electrical equipment reduces the possibility of fault transfer to metallic structures.

Continuous monitoring is another determining factor. Without periodic potential measurements and specialized technical evaluation, stray current corrosion may be confused with other mechanisms, delaying mitigation.

When to use insulating flanges in CP systems?

Insulating flanges are particularly recommended when multiple cathodic protection systems are located in proximity, or when a pipeline crosses property boundaries, pumping stations, or areas with different grounding systems. They are also critical at electrified railway crossings or in areas where nearby direct current networks exist.

In these cases, galvanic isolation electrically delineates the protected system and prevents external currents from interfering with CP performance. This improves the system’s energy efficiency and reduces the risk of forming corrosion cells due to localized discharge.

Fail-Safe technology and advanced solutions

In complex industrial applications, devices are required that not only electrically isolate but also provide overvoltage protection. Solutions developed by DAIRYLAND, known as the Fail-Safe Galvanic Isolator, combine direct current isolation with controlled conduction capability during high-energy events. This approach maintains electrical segmentation during normal operation while ensuring safety against lightning strikes or alternating current faults.

The integration of these solutions within a stray current mitigation strategy strengthens asset resilience and reduces the probability of catastrophic damage associated with unexpected electrical phenomena.

Strategic importance in critical assets

In the current context, where energy and transportation assets operate under increasing regulatory and environmental demands, galvanic isolation represents an investment in reliability. The proper combination of cathodic protection, electrical segmentation, and DC interference control makes it possible to maximize the service life of pipelines, tanks, and buried structures.

Modern integrity management recognizes that corrosion is not solely a chemical phenomenon, but also an electrical one. Controlling current paths is as important as selecting an appropriate coating or applying the correct protection potential.

Conclusions

Galvanic isolation is an essential technique for protecting industrial assets against stray currents and stray current corrosion phenomena. Its proper implementation allows control of electrical interference, optimization of cathodic protection, and improvement of operational safety during transient events.

By integrating devices such as insulating flanges, monolithic isolation joints, and isolation transformers within a coherent design, it is possible to significantly reduce risks associated with DC interference and overvoltage. Advanced solutions such as those proposed by DAIRYLAND under the Fail-Safe concept demonstrate that galvanic isolation is not merely a passive component, but a strategic element in the protection of critical infrastructure.

In an increasingly electrified industrial environment, understanding and correctly applying galvanic isolation is an indispensable condition for ensuring structural integrity and long-term operational sustainability.

References

1. Wikimedia Foundation. (n.d.). Galvanic isolation. Wikipedia. Retrieved from https://en.wikipedia.org/wiki/Galvanic_isolation
2. Riello UPS. (n.d.). What is galvanic isolation? Retrieved from https://www.riello-ups.com/questions/50-what-is-galvanic-isolation
3. DAIRYLAND Solutions: The Fail-Safe Galvanic Isolator