What is Galvanic Corrosion?

Galvanic corrosion is a persistent and damaging process that often plagues the industrial manufacturing and engineering sectors. When two dissimilar metals come into contact with an electrolyte, accelerated metal degradation begins to eat away at one of the metals, potentially compromising the integrity of vital equipment and infrastructure. Understanding galvanic corrosion isn't just about recognizing a problem — it's about protecting industrial assets and ensuring the safety and reliability of critical systems across numerous industries.

Related: What is Pitting Corrosion?

What to Know About Galvanic Corrosion

Understanding the Basics of Galvanic Corrosion

Galvanic corrosion, sometimes called bimetallic corrosion, is an electrochemical process when certain conditions align. This requires two different metals to touch, like steel bolts fastening an aluminum plate. When moisture is present — whether from rain, humidity, or industrial processes — it creates the perfect environment for galvanic corrosion to begin its destructive work.

This type of corrosion isn't a simple rusting process. Instead, it's more akin to a battery, where one metal sacrifices itself to protect the other. The key difference is that while batteries are designed for this purpose, galvanic corrosion often occurs unintentionally and can lead to catastrophic failures if left unchecked.

The Electrochemical Process Behind Galvanic Corrosion

To truly grasp how galvanic corrosion works, we need to understand its electrochemical nature. When two different metals connect in the presence of an electrolyte (like saltwater or even moisture in the air), they create a galvanic couple. The less noble metal becomes the anode, while the more noble metal becomes the cathode.

This electron transfer isn't just a simple exchange; it's part of a complex process where the anode material dissolves over time, weakening the metal structure. Meanwhile, the cathode remains relatively protected, creating an uneven deterioration that can be particularly dangerous in structural applications.

Environmental Contributing Factors

While the contact between dissimilar metals initiates galvanic corrosion, environmental conditions affect its severity and progression rate. Marine environments, with their constant exposure to saltwater, create particularly aggressive conditions for corrosion. The salt increases the conductivity of the electrolyte, accelerating the degradation process.

Temperature fluctuations and humidity levels also significantly impact corrosion rates. In industrial settings, where equipment might be exposed to varying temperatures and moisture levels throughout the day, these environmental factors can create ideal conditions for galvanic corrosion to thrive.

Identifying Galvanic Corrosion

Recognizing this type of corrosion early can prevent catastrophic failures and expensive repairs. The most visible signs often appear near the junction where dissimilar metals meet. Common indicators include white or gray powdery deposits, pitting or degradation of one metal while the other remains intact, and corrosion patterns that seem concentrated at specific connection points.

Engineers and maintenance professionals often rely on the anodic index when assessing corrosion risk between metal pairs. This index provides a numerical value for each metal's electrical potential, helping predict the likelihood and severity of corrosion when different metals come into contact. For instance, when stainless steel contacts aluminum, their significant difference in anodic index values indicates a high risk of galvanic corrosion. Visual inspections should focus on areas where metals with large anodic index differences meet, particularly in environments with high moisture exposure or chemical presence. Regularly monitoring these susceptible areas enables early detection and intervention before significant damage occurs.

What Problems Can Galvanic Corrosion Cause?

Galvanic corrosion can cause severe damage across various applications, from infrastructure to industrial equipment. Here are the key problems it creates:

Structural Issues

• Weakening of load-bearing components
• Reduction in material thickness
• Creation of stress concentration points
• Compromised joint integrity
• Deterioration of support structures
• Foundation and reinforcement damage

Performance Degradation

• Decreased electrical conductivity
• Reduced heat transfer efficiency
• Compromised mechanical properties
• Impaired system reliability
• Reduced operational efficiency
• Inconsistent equipment performance

Safety Concerns

• Unexpected component failure
• Leakage in fluid systems
• Compromised protective coatings
• Structural instability risks
• Safety system deterioration
• Equipment malfunction hazards

Economic Impact

• Increased maintenance costs
• Unplanned downtime expenses
• Shortened equipment lifecycle
• Premature replacement needs
• Higher repair frequency
• Lost production revenue
• Increased inspection requirements
• Rising insurance costs

These issues often translate into significant financial impacts through direct repair costs and indirect losses from operational downtime.

Industries Impacted by Galvanic Corrosion

Aviation & Aerospace

The aerospace industry faces unique challenges with galvanic corrosion due to its reliance on lightweight materials and exposure to diverse environmental conditions. Modern aircraft often combine aluminum alloys with titanium or steel components, creating numerous potential galvanic couples. The high stakes in aerospace applications mean that even minor corrosion issues must be addressed promptly and effectively. Aircraft experience dramatic temperature fluctuations and varying atmospheric conditions during flight, which can accelerate corrosion processes in untreated areas. Additionally, the increasing use of carbon fiber composites alongside traditional metals introduces new degradation challenges that require innovative protection strategies.

Oil & Gas

In the oil and gas sector, galvanic corrosion constantly threatens infrastructure integrity. The industry must contend with numerous scenarios where corrosion can develop from offshore platforms exposed to seawater to underground pipelines dealing with varying soil conditions. The presence of corrosive chemicals and high-pressure environments only compounds these challenges. Subsea equipment faces particularly aggressive conditions where the combination of deep-water pressure, salt water, and temperature variations accelerates corrosion rates. The complexity of modern extraction equipment, with its various metal alloys and components, creates multiple potential points that can undergo galvanic corrosion.

Clean Energy

The renewable energy sector faces its own set of galvanic corrosion challenges. Wind turbines, for instance, often combine different metals in their construction while being exposed to harsh environmental conditions. Solar installations must deal with the effects of weather exposure on their mounting systems and electrical connections. The emerging hydrogen energy sector introduces additional complexities, as hydrogen production and storage systems must withstand galvanic corrosion and hydrogen embrittlement. The drive for increased efficiency and lighter materials in renewable energy systems often necessitates using dissimilar metals, making corrosion protection a critical design consideration.

Construction & Infrastructure

From reinforced concrete structures to HVAC systems, the combination of diverse materials and exposure to moisture creates numerous opportunities for galvanic corrosion to develop in buildings and infrastructure projects. Infrastructure like bridges and utility systems are expected to have a long service life, preventing corrosion, which is even more critical since replacing or repairing affected components can be extremely costly and disruptive. The increasing use of smart building technologies and integrated electrical systems introduces new metal interfaces that must be protected against corrosion.

Marine

Perhaps no industry faces more severe galvanic corrosion challenges than the marine sector. Constant exposure to saltwater creates an aggressive environment for metal components. Ships, offshore platforms, and port facilities must all contend with the accelerated corrosion rates that marine environments promote. The combination of different water depths, temperatures, and oxygen concentrations creates varying corrosive conditions that must be addressed with comprehensive protection strategies. Introducing new hull materials and propulsion systems in modern vessels presents additional challenges for preventing corrosion while maintaining operational efficiency.

Preventing Galvanic Corrosion in Manufacturing

Material Selection and Coatings

Preventing galvanic corrosion starts with thoughtful material selection during the design phase. Engineers must consider both the functional requirements of components and their electrochemical compatibility. When dissimilar metals can't be avoided, proper protective measures are important. Understanding the galvanic series helps engineers predict potential corrosion risks and make informed decisions about material combinations. Even small changes in material selection can significantly impact industrial equipment's long-term durability and maintenance requirements.

Modern coating technologies offer effective barriers against galvanic corrosion. These coatings prevent electrolyte contact with the metal surface or provide sacrificial protection through specially designed formulations. The key lies in selecting the right coating system for specific operating conditions and ensuring proper application. Advanced coating systems can now be customized to specific environmental conditions, offering targeted protection against particular corrosive environments. Developing multi-layer coating systems has further enhanced protection capabilities, allowing for barrier and sacrificial protection in a single application.

Cathodic Protection

This technique harnesses the electrochemical principles that cause galvanic corrosion to protect valuable metal components. At the heart of this method are sacrificial anodes — specifically designed components made from highly reactive metals such as zinc, magnesium, or aluminum. These sacrificial anodes are intentionally installed to corrode in place of the more valuable metal structures they protect.

The process works by making the protected metal structure the cathode in the galvanic couple, while the sacrificial anode serves as the component that corrodes preferentially. For example, zinc sacrificial anodes are commonly employed in marine applications, where they corrode instead of the steel hull or other critical components. As these anodes gradually deteriorate, they can be replaced during routine maintenance, making them a cost-effective and reliable protection method. Successful cathodic protection relies on proper anode selection and strategic placement to protect the metal structure completely.

Protective Barriers and Insulation Techniques

Design strategies can also help prevent corrosion. Electrical isolation techniques, such as using non-conductive washers and gaskets between dissimilar metals, provide an effective first line of defense. Physical barriers between dissimilar metals, proper drainage to prevent electrolyte accumulation, and insulating materials are vital in comprehensive corrosion prevention. Advanced corrosion inhibitors can be integrated into these protection systems, providing an additional layer of defense in areas where complete electrical isolation isn't practical. Corrosion inhibitors are specialized chemical compounds that, when added to a liquid or coating, decrease the rate of metal oxidation by forming a protective film on metal surfaces.

Engineers must also consider the placement and orientation of components to minimize water traps and ensure proper ventilation in enclosed spaces. Implementing regular inspection points and maintenance access makes it easier to monitor potential corrosion sites and perform preventive maintenance. Advanced design software and modeling tools allow engineers to predict potential galvanic coupling points during the design phase, enabling proactive prevention strategies before manufacturing begins.

How Linde AMT Helps Combat Galvanic Corrosion

Linde Advanced Material Technologies (AMT) brings decades of expertise to the challenge of galvanic corrosion protection. Our advanced coating solutions incorporate cutting-edge materials science and application technologies to provide reliable protection across diverse industrial applications. We offer comprehensive solutions tailored to specific operational requirements, from thermal spray coatings to specialized surface treatments.

Our proprietary coating formulations are engineered to create effective barriers against corrosion while maintaining the operational performance of protected components. Through continuous innovation in our world-class Product Discovery Labs™, we develop and refine coating solutions that address emerging industry challenges, ensuring long-term protection against galvanic corrosion under even the most demanding conditions. Our SERMETEL® and SERMAGARD® coating systems offer exceptional resistance to corrosive environments while maintaining excellent adhesion and durability. These solutions are engineered to provide long-term protection for critical components in challenging operating conditions.

Why Choose Linde AMT for Your Coating Needs?

When protecting valuable industrial assets from corrosion, experience and expertise matter. Our global network of technical specialists combines deep materials science knowledge with practical application experience to deliver effective, long-lasting protection solutions. We understand that each application presents unique challenges, and we work closely with clients to develop customized protection strategies that address their specific needs. With over 50 years of coating technology experience and a proven track record across multiple industries, we provide complete solutions, including technical consultation, application support, and ongoing maintenance guidance. Our commitment to quality is reflected in our rigorous testing procedures and comprehensive quality control systems that ensure consistent, reliable protection for your critical components.

Contact our team today to discuss how our advanced coating solutions can help protect your assets and ensure long-term operational reliability. 

FAQs

Can galvanic corrosion occur without moisture?
No, galvanic corrosion requires an electrolyte (typically water or moisture) to facilitate the electrochemical reaction between the dissimilar metals.

What causes galvanic corrosion to accelerate?
Galvanic corrosion accelerates when there's a large potential difference between the metals involved, increased electrolyte conductivity (such as in salt water), and unfavorable anode-to-cathode surface area ratios.

How quickly does galvanic corrosion progress?
The rate of galvanic corrosion varies significantly depending on environmental conditions, metal combinations, and protective measures in place. It can range from months to years before visible damage appears.

What's the best way to prevent galvanic corrosion?
Prevention typically involves a combination of careful material selection, proper protective coatings, and design considerations that minimize or eliminate contact between dissimilar metals.