Understanding and Preventing Galvanic Corrosion

Galvanic corrosion occurs when dissimilar metals or materials are electrically connected in a corrosive environment. This results in one metal (the anode) corroding preferentially to protect the other (the cathode). The phenomenon is driven by differences in the metals’ open circuit potentials, which are summarized in the galvanic series. For example, zinc, with a potential around -1.1V, serves as an effective sacrificial anode for protecting materials like steel (approximately -0.6V) or stainless steel (around -0.2V). This fundamental principle is why zinc is widely applied as a protective coating in various industrial applications.

For further technical insight into galvanic corrosion and the galvanic series, consult resources such as AMPP International and the ASTM G71 standard.

The ASTM G71 Galvanic Corrosion Testing Process

The ASTM G71 standard outlines a flexible corrosion testing process that has become a benchmark for evaluating galvanic corrosion under controlled conditions. This method provides a reliable way to assess how dissimilar materials interact, both in laboratory settings and on actual field samples. It provides the basic guidelines for galvanic corrosion analysis which can then be tailored to specific materials, applications, and environments.

Key Applications of ASTM G71 Testing

• Comparison of Materials and Coatings:
  Evaluate how different metals and protective coatings interact. For example, testing may confirm that a zinc coating effectively sacrifices itself to shield a base metal such as steel or stainless steel from corrosive attack.
• Routine Product Testing:
  Manufacturers can routinely test products to ensure that galvanic interactions are within acceptable limits before shipment or installation, thereby enhancing overall product quality and longevity. For example, we regularly test aluminum materials to confirm they are within the expected open circuit voltage potentials, and then combine materials to assess the galvanic coupling.
• Research and Development:
  R&D teams can leverage ASTM G71 testing to optimize material selection and coating systems. Understanding galvanic behavior under simulated conditions helps develop more durable products and innovative corrosion prevention solutions.
• Failure Analysis:
  When corrosion-related failures occur, ASTM G71 testing can be used afterwards to confirm if galvanic corrosion was a contributing factor. This helps in diagnosing failures and/or planning corrective measures.

Advanced Testing Capabilities at US Corrosion Services

At US Corrosion Services, we go beyond standard testing. Our state-of-the-art facilities combine traditional ASTM G71 procedures with accelerated mechanical testing techniques, such as rising step load capabilities. This integrated approach enables us to simulate harsh service conditions and evaluate:

• Hydrogen Embrittlement:
  By combining mechanical loading with galvanic corrosion testing, we can assess how corrosion contributes to hydrogen embrittlement—a critical factor in the premature failure of high-stress components.
• Environmental Cracking:
  Our advanced testing methods help understand the role of galvanic corrosion in environmental cracking scenarios, providing a more comprehensive picture of material performance under realistic operating conditions.

This enhanced analysis not only identifies potential issues early but also guides effective preventative measures and mitigation practices.

Why Galvanic Corrosion Testing Matters

Understanding and mitigating galvanic corrosion is crucial in industries such as power generation, oil & gas, marine, and infrastructure. Proper testing per ASTM G71 allows engineers and maintenance teams to:

• Prevent Premature Failures:
  By identifying galvanic couples that could lead to accelerated corrosion, you can implement protective measures—such as applying a zinc coating—that prolong the lifespan of critical components.
• Optimize Material Selection:
  Informed material comparisons lead to better decisions when selecting metals and coatings for specific service environments.
• Ensure Compliance and Safety:
  Following recognized standards like ASTM G71 ensures that your corrosion testing is both scientifically sound and in line with industry best practices.

For further reading on galvanic corrosion, please refer to the Electrochemical Society publications and ASM International’s corrosion resources, amongst many other good options.

Partner with US Corrosion Services

At US Corrosion Services, we offer a complete suite of galvanic corrosion testing services tailored to your industry’s needs. Whether you require routine product testing, in-depth failure analysis, or advanced simulation of environmental conditions, our team of experts is ready to help.

Contact us today to learn more about our ASTM G71 testing capabilities, request a custom testing proposal, or schedule an on-site consultation: