New Coating Technologies Extending Aerospace Fastener Life

With the rising cost of factory-new aircraft hardware and increased competition over limited supply, aerospace engineers across the globe are consistently engaged in the pursuit of enhancing component longevity. For this, many focus on targeting the primary catalysts for fastener degradation and failure, which include galvanic corrosion, high-frequency vibration, and extreme fluctuating temperatures. As research and development efforts reach new milestones, a range of coating technologies and surface options are quickly emerging to bolster reliability in the face of common stressors.

Put simply, fastener coatings act as a primary defense for surfaces, offering a barrier that can withstand the environmental and mechanical forces typical of flight much better than a raw metal surface alone. While coatings have long existed for fasteners and other hardware components, recent breakthroughs in material science and treatments have revolutionized average capabilities for service live extension. If you are interested in learning more about the notable fastener coating developments occurring across the industry, read on as we provide an informational overview.

Current Trends in Aerospace Fastener Coatings

While there is a range of developments currently taking the industry by storm, the most dominant trend as of recent is the continued push toward environmentally sustainable and high-performance coatings. From enhanced platings that follow modern military standards for chemical resistance to a range of strain-relief and friction-control coatings that harness emerging ceramic materials, many new technologies and offerings are coming about to extend the interval between maintenance and overhaul cycles. For those who are involved in the industry, some of the most notable trends that are a part of this evolution include:

• Zinc-Nickel (Zn-Ni) Plating: Zn-Ni plating has debuted as a great alternative to cadmium, offering operators a solution for superior corrosion resistance without facing the typical drawbacks of toxicity or hydrogen embrittlement. As a result, these cadmium-free aerospace coatings prove great in saline environments.
• Ceramic-Metallic (Cermet) Coatings: With cermet materials, fasteners can achieve reliable levels of thermal stability that are sufficient for the hot zones of engines. Unlike more conventional options, the use of this material mixture ensures that oxidation is avoided when temperatures surpass 500°C.
• Diamond-Like Carbon (DLC): When exceptional surface hardness and a low-friction coefficient is desired to mitigate galling effects, engineers will now regularly turn to advanced, diamond-like carbon materials to establish a robust and low-friction surface. Beyond longevity, these coatings also eliminate the need for additional wet lubricants.
• Nano-Composite Coatings: With modern, molecular-level engineering capabilities being more feasible, manufacturers are able to improve the density and uniformity of many fastener protective layers to reduce negative attributes like porosity and moisture ingress risk.
• Self-Healing Polymers: As one of the most fascinating developments as of late, self-healing polymers that are being added to fasteners incorporate micro-capsules that rupture upon the occurrence of surface damage, releasing sealants to prevent the spread of localized corrosion.

While only a handful of examples, many other developments are rapidly reshaping aerospace coatings and opening new avenues of enhancing longevity and long-term performance.

Standards and Specifications Dictating Coating Quality

The evolution of industry standards goes hand-in-hand with fastener coating development, with engineers following rigorous specifications set forth by government bodies and industry committees alike to achieve the level of uniformity and safety that is expected in aerospace operations. While Aerospace Standards (AS) and Military Standards (MS) often dominate in terms of demand with a major focus placed on fastener performance and interchangeability, coatings are also regularly dictated by guidelines set forth by National Aerospace Standards (NAS) and the Society of Automotive Engineers (SAE). In many cases, compliance with any one of these aerospace coating standards can be non-negotiable, as they tend to be required in contracts or purchase orders to ensure the level of engineering quality that is needed for confidence in longevity.

Notable Standards for Aerospace Coatings

• AMS2417: As the industry-standard specification for Zinc-Nickel alloy plating, AMS2417 sets resistance benchmarks for nickel content and corrosion resistance that benefit aerospace operations.
• NAS4006: This NAS specification covers requirements for aluminum-pigmented coatings that are applied to fasteners used in aluminum airframes to prevent galvanic corrosion.
• ASTM B117: Operators follow this standardized salt spray testing method to verify the longevity of corrosion protection for various coatings.
• MIL-STD-870: This Military Standard specifically addresses cadmium plating requirements, primarily being maintained for legacy platform maintenance needs and specific defense applications.
• AS9100/AS9120: These quality management standards are common for distributors and suppliers engaged in aerospace fulfillment, ensuring that any coated fasteners follow industry expectations for inventory management, quality control, and export compliance. 

While many projects will specify whether or not specific industry coating standards must be addressed, organizations can always benefit from familiarizing themselves with the various options available on the market and the respective benefits they each provide.

What Buyers Should Consider When Shopping for Coated Fasteners

When buyers evaluate corrosion-resistant aircraft fasteners or any other coated hardware of need, there are a number of basic factors that should be considered to ensure the best fit is found. For example, fasteners used in engines and other areas exhibiting extreme heat will necessitate very different coatings and characteristics when compared to the hardware that will be on wings and skin structures that are more threatened by moisture and salt. With concerns like these, any purchase should always be preceded by careful evaluation of requirements. Generally speaking, any purchasing decision should begin with factoring in elements like:

• Environmental Compatibility: Whether the concern is for assemblies to be safeguarded from corrosion, vibration, temperature fluctuation, or a mixture of these stressors, the process of aligning fastener coatings with operational needs cannot be overlooked.
• Installation Behavior: Surface treatments regularly alter how a fastener may behave during assembly, potentially affecting its geometry or compatibility with surrounding metals when compared to a raw component. This matters when the application requires more consistent installation conditions and/or closer control over torque response.
• Hydrogen Embrittlement Relief: For any aerospace fasteners made from high-strength steel, confirm that mandatory baking processes have been carried out after plating to mitigate the risk of brittle failure.
• Removal Conditions: Dry-film and anti-galling finishes can make disassembly easier during maintenance, which is especially useful when hardware must be removed without harming adjacent surfaces.
• Traceability and Quality: For confidence in the reliability of coated fasteners and to address any concerns for compliance, obtaining proper documentation that conveys information ranging from the original manufacturer of an item to its current condition is important.

With the diversity of aerospace operations, investment decisions in any emerging aerospace coating solutions should always be based on careful consideration for the unique objectives of one’s organization or airline.

Source Coated Aerospace Fasteners Through a Reliable Procurement Channel

With a better understanding of modernized aerospace coating technologies and strengthening industry standards that aim to enhance fastener longevity, professionals can approach procurement with better insight into available solutions. As you begin to kick off your own fulfillment endeavors and seek out a purchasing platform for reliable and efficient solutions, turn to Fastener World 360 as your single-source solution. 

Owned and operated by ASAP Semiconductor, a leading aerospace distributor, Fastener World 360 is replete with quality-assured hardware that meets legacy and next-gen platform needs alike. With curated catalogs offering access to over 6 billion unique listings, be sure to explore our purchasing platform at your leisure while leveraging our user-friendly lookup tools to save time. For any pricing inquiries or requests, we invite you to fill out and submit a Request for Quote (RFQ) form through our website. Our responses are always quick, so be sure to connect with us today!