Eastern Gate Team

WHAT IS ZINC FLAKE COATING?Zinc flake coating is a high-performance, non-electrolytic corrosion-protection system composed of zinc and aluminium flakes dispersed within an inorganic binder. Engineered for exceptional durability, this thin-film coating offers superior corrosion resistance—making it particularly suitable for high-strength fasteners used in demanding environments.Developed in the 1970s to address rising industrial requirements for robust, environmentally responsible corrosion protection, zinc flake technology quickly became a preferred solution for automotive, renewable energy, and heavy-industrial applications. Its breakthrough advantage lies in the elimination of hydrogen embrittlement risk, a critical concern in electroplating processes when dealing with fasteners above 1000 MPa tensile strength.By the 1980s and 1990s, the technology gained global adoption driven by its excellent red-rust resistance, uniform coverage, and compliance with emerging environmental regulations restricting hexavalent chromium. Today, zinc flake systems have become a cornerstone of corrosion-resistant engineering, delivering long-term protection while maintaining a clean, metallic aesthetic even after prolonged exposure to harsh conditions.How Zinc Flake Coatings Are AppliedThe application of zinc flake coatings involves a controlled, multi-stage process designed to ensure consistent film build, strong adhesion, and reliable corrosion performance.1. Surface PreparationFasteners undergo meticulous cleaning to remove oils, rust, and contaminants. Depending on specifications, preparation may include:<ul><li>Degreasing</li><li>Shot blasting for mechanical roughening</li><li>Phosphating to form a conversion layer promoting adhesion</li></ul>A well-prepared surface is critical for achieving uniform film formation and long-term durability.2. Pre-TreatmentChemical pre-treatments may be applied to enhance coating adhesion and stabilise the substrate surface. This step ensures the coating bonds uniformly and performs consistently in corrosive environments.3. Coating ApplicationZinc flake coatings are applied using non-electrolytic methods tailored to part geometry:<ul><li>Dip-Spin</li><li>Ideal for bolts, nuts, and washers processed in bulk. Components are dipped into the coating slurry and centrifuged to achieve controlled film thickness.</li><li>Spray Application</li><li>Suitable for large or complex components requiring directional coating or targeted film build.</li><li>Dip-Drain</li><li>Used for heavier or oversized parts that cannot be spun, ensuring full coverage without excessive buildup.</li></ul>4. CuringCoated components are baked at 200°C to 320°C, allowing the inorganic binder to harden into a dense, lamellar shield. The result is a strong, adherent metallic layer capable of providing exceptional corrosion protection with minimal thickness.How Zinc Flake Coatings Prevent CorrosionZinc flake systems provide corrosion protection through two complementary mechanisms:1. Barrier ProtectionThe lamellar arrangement of zinc and aluminium flakes forms a tightly interlocked film that blocks:<ul><li>Moisture</li><li>Oxygen</li><li>Salts</li><li>Industrial pollutants</li></ul>This barrier significantly slows down corrosion initiation.2. Sacrificial (Cathodic) ProtectionZinc acts as a sacrificial anode. When the steel substrate is exposed or scratched:<ul><li>Zinc corrodes preferentially</li><li>The steel surface remains protected</li><li>Red rust formation is delayed significantly</li></ul>Aluminium flakes enhance thermal stability and improve the coating’s mechanical integrity.Free from Hydrogen EmbrittlementBecause zinc flake coatings are non-electrolytic, they do not generate hydrogen during application—making them the safest corrosion-protection method for high-strength fasteners (≥10.9 grade).In standardized testing, zinc flake coatings routinely achieve &gt;1000 hours of red-rust resistance in salt spray chambers (ASTM B117).Advantages of Zinc Flake Over Traditional Coatings1. No Hydrogen Embrittlement RiskIdeal for high-strength fasteners, unlike electroplating which can introduce hydrogen into the steel matrix.2. Superior Corrosion ResistanceAchieves exceptional salt spray performance, outperforming hot-dip galvanizing (HDG) and electroplated zinc in aggressive environments.3. Thin, Uniform FilmTypical coating thickness of 8–20 µm maintains:<ul><li>Thread tolerance</li><li>Assembly performance</li><li>Dimensional accuracy</li></ul>HDG, by comparison, is significantly thicker and may interfere with thread engagement.4. High Temperature StabilityMaintains performance at temperatures up to ~320°C, suitable for automotive under-hood, powertrain, and industrial applications.5. Environmentally CompliantModern zinc flake systems are:<ul><li>Chromium(VI)-free</li><li>RoHS compliant</li><li>REACH compliant</li></ul>This supports sustainability goals and regulatory requirements.6. Mechanical and Chemical DurabilityThe metallic, lamellar structure provides:<ul><li>Excellent abrasion resistance</li><li>UV stability</li><li>Chemical resistance</li></ul>Enhancing performance in outdoor and industrial settings.Key International Standards for Zinc Flake CoatingsISO 10683:2018Fasteners — Non-electrolytically Applied Zinc Flake Coating SystemsDefines performance criteria, test requirements, and application guidelines for zinc flake coatings on fasteners including bolts, screws, studs, nuts, washers, clips, and pins.ASTM F3393-24Standard Specification for Zinc-Flake Coating Systems for FastenersSpecifies classification, film build, performance characteristics, and corrosion requirements for zinc flake coatings on inch-series and metric fasteners (≥6 mm / 0.250”).ConclusionZinc flake coatings represent a modern, high-performance corrosion-protection technology specifically engineered for the evolving demands of automotive, construction, energy, and industrial sectors. Offering superior resistance to red rust, thin uniform layers, zero hydrogen embrittlement risk, and full compliance with ISO and ASTM standards, zinc flake systems deliver reliability where it matters most.As industries increasingly prioritise durability, sustainability, and performance, zinc flake coating stands out as a future-ready solution—providing strong defence, long service life, and unmatched suitability for high-strength fastening systems.

Zinc flake coating is a high-performance, non-electrolytic corrosion protection system designed for demanding applications. Its thin, uniform layer of zinc and aluminium flakes delivers exceptional corrosion resistance, eliminates hydrogen embrittlement risk, and meets strict environmental standards. Strong, lightweight, and highly durable, it has become the preferred choice for high-strength fasteners across construction, energy, automotive and industrial sectors. 

Zinc flake coating is a high-performance, non-electrolytic corrosion protection system designed for demanding applications. Its thin, uniform layer of zinc and aluminium flakes delivers exceptional corrosion resistance, eliminates hydrogen embrittlement risk, and meets strict environmental standards. Strong, lightweight, and highly durable, it has become the preferred choice for high-strength fasteners across construction, energy, automotive and industrial sectors.

Zinc Flake Coating for Fasteners: Thin Film, Strong Defence