Coated Fasteners
Manufacturer
India · Mumbai
Coating vs Solid Alloy — Where the Protection Actually Lives
Every corrosion-resistant material we’ve covered elsewhere — SS 316L, super duplex, Hastelloy B-3 — achieves its corrosion resistance as a property of the bulk alloy itself, present uniformly through the entire cross-section of the part. A coated fastener works on a fundamentally different principle: an ordinary carbon or low-alloy steel base is manufactured to full strength first, and a separate protective layer is then applied to the surface — zinc, a zinc-aluminum flake system, or a phosphate conversion layer — to protect the steel underneath from the environment.
This distinction carries a genuine, practical trade-off. A coating is substantially less expensive than manufacturing the entire fastener from a solid corrosion-resistant alloy, and is entirely adequate for the large majority of general corrosion protection needs. But because the protection is a discrete surface layer rather than a bulk material property, a coating can be damaged, worn through, or under-specified in thickness in a way that a solid stainless or exotic alloy fastener’s protection simply cannot be — scratch through a zinc coating deeply enough, and the exposed steel beneath corrodes normally.
This is exactly why coating selection matters as much as material grade selection — a genuinely important sizing decision this page treats with the same care given to alloy grade selection elsewhere on our site. High-strength coated fasteners carry an additional manufacturing consideration entirely their own — hydrogen embrittlement risk — covered in full detail immediately below.
Why Coated Fasteners — Genuine Value for General Corrosion Protection
Substantially Lower Cost Than Solid Alloy
A carbon steel base with a protective coating is significantly less expensive than manufacturing the same fastener from solid stainless or exotic alloy — the correct choice wherever a coating’s protection level is genuinely sufficient.
Multiple Coating Systems for Different Severity
From light-duty zinc electroplating through heavy-duty hot-dip galvanizing to advanced zinc flake systems, coating selection can be matched precisely to service environment without paying for more protection than needed.
Base Steel Strength Unaffected by Coating Choice
Because the coating is applied to an already-manufactured steel fastener, the full range of carbon and alloy steel property classes — including high-strength Grade 8.8 and 10.9 — remains available under any coating system.
Decorative and Functional Finish Options
Beyond corrosion protection, coating choice also determines appearance and friction characteristics — from bright zinc’s clean look to specialised low-friction coatings for controlled torque-tension applications.
Hydrogen Embrittlement — A Delayed Failure Risk, Not a Cosmetic Concern
Electroplating processes work by passing an electric current through a plating bath, and this same electrochemical process can introduce atomic hydrogen into the surface of the steel being plated. In lower-strength fasteners this hydrogen typically causes no practical problem. In high-strength fasteners — commonly Grade 8.8 and above — this absorbed hydrogen can migrate to areas of internal stress within the steel and cause hydrogen embrittlement: a real, well-documented failure mode where the fastener can fracture suddenly under sustained load, sometimes days or even weeks after installation, with no visible warning beforehand.
This is precisely why post-plating baking — a controlled heat treatment applied shortly after electroplating — is mandated for high-strength electroplated fasteners: baking drives out the absorbed hydrogen before it can migrate to stress concentration points and cause delayed cracking. Baking time and temperature are specified and verified per ASTM F1940, and this step is not optional or cosmetic — it is the specific manufacturing control that exists because the underlying risk is real.
Zinc flake coating systems are increasingly specified on high-strength fasteners specifically to avoid this risk category entirely — because zinc flake coatings are mechanically applied and cured rather than electrolytically deposited, they do not introduce hydrogen into the steel in the same way electroplating does, removing the embrittlement risk at its source rather than managing it after the fact through baking. Akbar Fasteners manufactures high-strength electroplated fasteners with documented, verified baking per ASTM F1940 as standard practice, and can recommend zinc flake coating as an alternative wherever embrittlement risk is a primary design concern.
Zinc Electroplating vs Hot-Dip Galvanizing vs Zinc Flake
All three use zinc’s sacrificial (cathodic) protection principle — zinc corrodes preferentially, protecting the steel beneath even at small breaks in the coating — but the application method and resulting thickness differ substantially.
Zinc Electroplating
A thin zinc layer (typically 5–25 microns) deposited electrolytically, giving a bright, uniform appearance suitable for general indoor and light outdoor duty. The most economical zinc coating option, but with the shortest service life and hydrogen embrittlement risk on high-strength grades.
Hot-Dip Galvanizing (HDG)
A much thicker zinc coating (typically 50–100+ microns) formed by immersing the fastener in molten zinc, providing genuinely long-term outdoor and structural protection through sacrificial zinc corrosion, at the cost of dimensional buildup that must be accounted for in thread fit.
Zinc Flake (Dacromet / Geomet-type)
Overlapping zinc-aluminum flakes suspended in an inorganic binder, mechanically applied and oven-cured rather than electroplated — delivering strong corrosion resistance without the hydrogen embrittlement risk electroplating carries, making it the preferred choice for high-strength fasteners.
Coated Fastener Grade & Coating Options
Base steel property class is selected independently of coating — coating governs environmental protection, base grade governs mechanical strength.
Coated Fasteners Application Areas
Wherever general-to-heavy corrosion protection is needed without the cost of a solid corrosion-resistant alloy.
Structural Steel & Construction
outdoor structural fastening
Automotive Assembly
embrittlement-sensitive components
General Machinery
indoor equipment fastening
Fencing & Outdoor Hardware
long-term outdoor exposure
Appliance & Electronics
panel and enclosure assembly
Agricultural Equipment
outdoor exposed machinery
Rail & Heavy Transport
vibration-resistant coated hardware
General Industrial Assembly
full range of coating options
Coated Fastener Standards Coverage
Same ISO 9001:2015 quality system as our complete fastener range. Coating thickness and, where applicable, hydrogen embrittlement baking verified on every production lot.
Complete Documentation Package
Base Grade Stated
Per Applicable Standard
Baking Certificate (Gr. 8.8+)
Conformance
On Request
Related Materials & Fastener Types
Coated fasteners for cost-effective general protection. Solid alloy fasteners where damage-tolerant, uniform corrosion resistance is required instead. Full bolt and nut range across all coating and material options.
SS 316L Fasteners
The solid-alloy alternative where corrosion resistance must survive surface damage or abrasion that would compromise any coating.
View SS 316L Fasteners →Super Duplex Fasteners
For the most severe chloride environments where even a heavy-duty coating would be insufficient and a solid high-PREN alloy is required.
View Super Duplex →Full Bolt Range
Complete bolt manufacturing capability at Akbar Fasteners, available across every coating system covered on this page plus solid alloy options.
View Bolt Range →Full Nut Range
Matched nuts available in the same coating systems as this page’s bolt and screw coatings, for a consistent finish across the joint.
View Nut Range →Need Coated
Fasteners?
Coating type · base grade · thread size · quantity. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Export: +91 8696 32 4646 · Support: +91 800 9315 333 · export@akbarfasteners.in