Guide to nylon washers for galvanic isolation

Nylon washers are commonly specified as electrical isolation washers in assemblies that join dissimilar metals. By electrically isolating fasteners from adjoining components, they limit corrosion-related damage at connection points and help preserve surface integrity and joint performance over time. This function is particularly important in environments exposed to moisture, condensation, or other corrosive conditions, where direct metal-to-metal contact can accelerate material degradation. In this guide, we'll take a closer look at:

What is galvanic corrosion?
What is galvanic isolation?
Why nylon washers are effective for galvanic isolation
Types of nylon washers 
When to use nylon washers for galvanic isolation
Conclusion and expert resources

What is galvanic corrosion?

Galvanic corrosion is an electrochemical process. It occurs when two dissimilar metals are in direct electrical contact with an electrolyte, such as water, moisture, or salt spray. Each metal has a different electrochemical potential, which generates an electrical current between them. The less noble (more reactive) metal becomes the anode and corrodes, while the more noble metal acts as the cathode and remains protected.

This type of corrosion commonly occurs in environments where moisture is present, including marine, outdoor, industrial, and infrastructure settings. Small amounts of humidity can allow corrosion to develop gradually over time. The process often accelerates material degradation at contact points, especially where fasteners join dissimilar metals.

If left unaddressed, galvanic corrosion can weaken structural connections, compromise surface finishes, and reduce the overall service life of assemblies. Understanding how and why this process occurs is a critical first step in effective galvanic corrosion prevention.

What is galvanic isolation?

Galvanic isolation is the practice of electrically separating dissimilar conductive materials to prevent the flow of current between them. By breaking the electrical path that would otherwise form at a contact point, galvanic isolation helps stop the electrochemical reaction that leads to corrosion.

In mechanical and structural assemblies, galvanic isolation focuses on eliminating direct metal-to-metal contact at joints, fasteners, and connection points. Electrical continuity between dissimilar metals in the presence of an electrolyte produces galvanic action at the contact interface. Corrosion damage is commonly observed at unisolated joints and fastener locations.

In engineering design, galvanic isolation is applied as a control measure for galvanic corrosion prevention by limiting electrical continuity. It does not describe a specific product or material, but rather a design approach aimed at controlling electrical continuity between components. Understanding galvanic isolation provides the framework for evaluating electrical isolation washers, insulating spacers, and other non-conductive elements, which are addressed in later sections.

Why nylon washers are effective for galvanic isolation

Nylon is a non-conductive material that prevents electrical current from passing between dissimilar metals. By eliminating direct metal-to-metal contact, nylon insulating washers interrupt the electrical path required for galvanic corrosion to occur, making them a reliable solution in assemblies exposed to moisture, humidity, or corrosive environments.

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Nylon washers do not corrode or oxidise under normal service conditions and are resistant to many common chemicals. Unlike metal washers, they don’t contribute to material loss or surface attack at fastening interfaces. As a result, separation at the joint is maintained without changes in washer geometry or performance over time.

Nylon washers separate fastener heads from adjoining surfaces. Contact between metal components is avoided at the joint interface. Minor movement at the connection is absorbed by the washer material, limiting surface wear under vibration or cyclic loading. Nylon washers are used where electrical separation is required as part of galvanic corrosion prevention.

Feature	Nylon washers	Metal washers
Electrical conductivity	Non-conductive, provides effective electrical isolation	Conductive, can complete an electrical circuit
Galvanic corrosion risk	Eliminates metal-to-metal contact, supporting galvanic corrosion prevention	Can accelerate galvanic corrosion when used with dissimilar metals
Corrosion resistance	Will not rust, oxidise, or corrode over time	Susceptible to rust, oxidation, and galvanic attack
Long-term performance	Maintains isolation and spacing throughout service life	Performance can degrade as corrosion develops
Surface protection	Protects finishes by preventing direct contact	Can damage coatings and bare metal surfaces
Vibration absorption	Absorbs vibration and reduces wear	Transfers vibration directly
Weight	Lightweight	Heavier
Maintenance requirements	Low maintenance	May require inspection or replacement over time

For a deeper understanding of these components, we urge you to check out The complete guide to washers.

Types of nylon washers

Our nylon fastening components are available in configurations to suit different load, spacing, and isolation requirements. Selecting the appropriate type depends on how the washer is used within the assembly and the level of electrical separation required.

When to use nylon washers for galvanic isolation

Nylon washers should be used for galvanic isolation in environments where moisture, humidity, or corrosive elements are present. In these conditions, nylon insulating washers help prevent electrical continuity between metal components, reducing the risk of corrosion at joints, fasteners, and contact points. But there are also other reasons these plastic washers make sense. 

Summary

Application scenario	Why nylon washers are recommended
Dissimilar metals in contact	Prevent electrical continuity and interrupt galvanic reactions
Moist or corrosive environments	Do not rust, oxidize, or degrade over time
Outdoor or marine-adjacent installations	Maintain isolation despite humidity and exposure
Electrical or electronic assemblies	Provide reliable electrical separation without conductivity
Coated or finished surfaces	Protect finishes by preventing metal-to-metal abrasion
Weight-sensitive or compact designs	Lightweight solution without sacrificing isolation
Long-term, low-maintenance systems	Reduce inspection, replacement, and corrosion-related failures

Our experts explain more in When to use plastic washers. You can also learn more in our guide, Differences between nylon and acetal.

Conclusion and expert resources

Galvanic corrosion is a persistent challenge in assemblies that combine dissimilar metals, particularly in environments exposed to moisture or corrosive elements. Understanding how galvanic corrosion occurs, and how galvanic isolation interrupts this process, is essential for designing durable and reliable systems. Nylon washers offer a practical and effective means of achieving electrical isolation at fastening points without introducing additional corrosion risks.

Nylon washers are non-conductive and do not corrode under typical service conditions. When used at fastening points, they provide electrical separation without introducing additional galvanic interactions or surface degradation.

For further guidance, we recommend you use these resources;

Polymer-insulated bolted joints and galvanic corrosion mitigation
A peer-reviewed academic article showing how polymer insulation in bolted joints significantly reduces galvanic corrosion depth and preserves joint integrity.

ISO/DIS 16364 – Guidelines for avoiding galvanic corrosion
An international guideline (in draft/standard form) that outlines engineering best practices for avoiding galvanic corrosion in design, including methods to suppress corrosion by interrupting electrical contact between dissimilar conductive materials.

ASTM corrosion standards and guides 
A comprehensive set of industry-recognized standards covering corrosion testing methods, including those relevant to galvanic corrosion evaluation and prevention.

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Free CADs are available for most solutions, which you can download. If you’re not quite sure which anti-corrosion washers will work best for your application, our experts are always happy to advise you. Whatever your requirements, you can depend on fast dispatch. 

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Questions?

Email us at sales@essentracomponents.co.uk or speak to one of our experts for further information on the ideal solution for your application at 0345 528 0474.