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Posted on March 3, 2026 Arian Lobo Aviation
Moisture, salt, industrial chemicals, and temperature fluctuations can all initiate corrosion on fasteners if such conditions are not properly accounted for, gradually compromising the integrity of joints in an assembly. While choosing the correct base material for desired hardware is an essential first step of any procurement process, surface coatings are also necessary to consider for their ability to dramatically extend average service life. With a wide array of approaches to implementing fastener coatings, read on as we provide an overview of the most common options and their ideal applications.
Zinc electroplating is one of the most popularly leveraged finishes for carbon steel and alloy steel fasteners, offering ample hardware protection against common environmental stressors. The process of implementing this plating involves immersing fasteners in an electrolyte solution that contains zinc salts before applying an electrical current to deposit zinc ions in a thin coating. Because zinc is more anodic than steel, it corrodes first when exposed to moisture and oxygen, serving as a sacrificial barrier for the underlying metal.
It is important to know that during electroplating, hydrogen may be generated as a byproduct of electrochemical reactions and possibly absorbed into the steel surface. This can lead to hydrogen embrittlement, a condition that reduces strength and may cause cracking under sustained or cyclic loads. Embrittlement is primarily a concern for high-strength fastener variants, so post-plating baking is typically required for these options to drive out any absorbed hydrogen.
This coating is economical and dimensionally consistent, but it is not intended for prolonged outdoor or marine exposure without additional protective treatments. For these environments, chromate conversion coatings that react with the zinc layer can be applied at the end of treatment. By itself, zinc plating performs best in indoor, mildly corrosive environments where exposure to moisture is limited.
Hot-dip galvanizing offers significantly more protection than basic zinc plating. During this process, carbon or alloy steel fasteners are immersed in molten zinc heated to approximately 450 degrees Celsius. At this temperature, the zinc reacts chemically with the iron in the fastener, causing iron and zinc atoms to diffuse into one another and form a series of tightly adherent zinc-iron alloy layers.
Above these alloy layers, a final outer layer of relatively pure zinc solidifies as the fastener is withdrawn from the bath. The outer zinc layer will corrode preferentially to the underlying steel, while the harder zinc-iron alloy layers beneath it continue to display resistance to abrasion or mechanical damage.
Because hot-dip galvanizing produces a relatively thick zinc coating, it offers superior longevity, especially for structures in high-humidity and coastal environments. However, this means that it is a better fit for larger-diameter fasteners or applications where adjustments can easily be made to accommodate the added coating thickness. Generally, hot-dip galvanizing is not suitable for stainless steel or non-ferrous metals.
Mechanical plating is another zinc-based coating process. For this approach, fasteners are placed in a rotating barrel with zinc powder, glass beads, water, and chemical promoters. As the barrel rotates, impact energy causes zinc particles to cold-weld onto the steel surface. The resulting coating offers corrosion resistance comparable to electroplated zinc while maintaining more consistent mechanical properties.
No electrical current is used for mechanical plating, so hydrogen generation is significantly reduced and leaves high-strength carbon and alloy steel fasteners that are treated with it much less susceptible to embrittlement. For this reason, mechanical plating is frequently employed for fasteners placed in automotive, heavy equipment, and structural applications.
Zinc-nickel coatings build upon traditional zinc electroplating by incorporating approximately 12% to 15% nickel into the deposited layer. The inclusion of nickel significantly enhances resistance to corrosion in chloride-rich environments, such as those exposed to road deicing salts, coastal air, or salt spray. After plating, these coatings are regularly treated with a passivation layer, a thin chemical conversion film that stabilizes the alloy and slows the formation of corrosion.
Zinc-nickel coating is perfect for automotive, aerospace ground support, and industrial machinery applications that demand durable fasteners where the use of stainless steel would otherwise alter mechanical properties or is simply not in budget.
Applied through electroplating, cadmium plating forms a thin, uniform metallic layer that offers outstanding sacrificial corrosion protection and inherent lubricity. One of its distinguishing advantages is its favorable galvanic compatibility with aluminum, which is helpful in mixed-metal assemblies.
While effective, cadmium is toxic and environmentally regulated, so many industries have transitioned to alternative coatings when feasible. However, it still finds use in aerospace and defense sectors on high-strength steel fasteners where preventing degradation is vital.
Unlike metallic coatings that rely on sacrificial action, polymer systems form a non-porous barrier that prevents corrosive agents from ever contacting the base material, while also protecting against other forms of wear. Formulated from epoxy, polyurethane, fluoropolymer, or other similar resins, these materials are applied using dip-spin or spray methods and cured to harden and properly adhere to the substrate. Additionally, some formulations incorporate zinc flake within the resin matrix for supplemental sacrificial performance. Pigments may also be added into the coating as a visual indicator of the fastener’s grade.
Polymer coatings are most often applied to carbon or alloy steel fasteners, but they may also be used on stainless steel where additional chemical resistance, reduced friction, or color coding is required. Because of their favorable characteristics, they are specified for fasteners across marine structures, renewable energy systems, infrastructure projects, and other areas exposed to aggressive atmospheric conditions.
More than evaluating environmental exposure, it is incredibly important to consider how selected coating will interact with surrounding materials. When two dissimilar metals are in contact and exposed to an electrolyte–such as water containing dissolved salts–galvanic corrosion can occur. To ensure that anti-corrosion fasteners perform as intended:
From economical zinc plated fasteners to polymer coated variants, each of these fastener surface coatings serve a specific purpose within modern engineering and construction. Regardless of which option best suits your needs, World of Fasteners is sure to have products worth considering. All customers, from those broadly seeking corrosion resistant bolts to those only looking for offerings from a particular galvanized hardware supplier, can benefit from our comprehensive selection of top-quality fasteners. To learn more about our array of products, sourcing support, and commitments, feel free to check out World of Fasteners for yourself and get in touch with our helpful team.
We hope that you will visit us again the next time you need hardware and fasteners parts and make us your strategic purchasing partner.
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