Guide to Hot Dip Galvanized Structural Fasteners

When it comes to structural integrity, outdoor performance, and long-term durability, few components work harder, or get less recognition, than the fasteners holding it all together.

At Eurolink Fastener Supply Service, we specialize in hard-to-find and high-performance metric fasteners, including Hot Dip Galvanized (HDG) structural bolts. These fasteners offer the strength of Class 10.9 steel combined with one of the best corrosion-resistant coatings in the industry, making them the go-to solution for infrastructure and high-stress outdoor projects.

Whether you're an engineer, project manager, or distributor looking for reliable structural hardware, this guide breaks down everything you need to know about HDG metric fasteners: from how they’re made to where they’re used and how Eurolink can help you source them quickly and confidently.

What Are Hot Dippped Galvanized Structural Fasteners?

Structural fasteners, such as hex bolts, nuts, and washers, are built to handle heavy loads and high-stress connections. When hot-dip galvanized, these fasteners are coated with a thick layer of zinc by immersing them in molten zinc at over 800°F. This creates a durable, corrosion-resistant layer ideal for long-term outdoor use.

Common HDG Structural Fasteners We Stock:

• Hex Bolts: EN 14399-4 (replaces DIN 6914)
  
  
• Nuts: EN 14399-4 (replaces DIN 6915)
  
  
• Washers: EN 14399-6 (replaces DIN 6916)
  
  
• Class: 10.9 (high-strength alloy steel)

Eurolink stocks a wide range of these parts from M12 to M30 in a hot-dip galvanized finish, with a plain finish available upon request. MTRs (Material Test Reports) are kept on file for all structural items.

Why Hot Dip Galvanization Matters

Corrosion Protection Where It Counts

HDG fasteners are essential in outdoor and infrastructure applications, where moisture, humidity, and environmental exposure threaten uncoated steel. Compared to standard zinc-plated fasteners, hot dip galvanizing creates a coating 5–12 times thicker, offering decades of protection.

While salt spray testing (EN ISO 9227) is commonly used to test coatings, it’s not reliable for HDG. That’s because salt spray tests prevent the natural passivation layer from forming, underestimating HDG’s performance. According to industry sources, HDG coatings of 50μm can provide 20–30 years of corrosion resistance, especially in rural or moderately corrosive environments.

Cost-Effective vs. Stainless Steel

Some may ask, “Why not just use stainless steel?”

The answer: while stainless steel offers corrosion resistance throughout the material, it’s significantly more expensive and not as strong as Class 10.9 steel. HDG on 10.9 fasteners delivers a balance of mechanical performance, cost efficiency, and corrosion resistance, making it the preferred choice in most structural and infrastructure applications.

Where Are HDG Structural Fasteners Used?

Eurolink’s HDG fasteners are commonly used in high-load and high-corrosion environments such as:

• Bridges and Overpasses
  
  
• Transmission Towers & Substations
  
  
• Solar Panel Racks and Wind Farms
  
  
• Industrial Buildings and Steel Frameworks
  
  
• Coastal and Marine Infrastructure
  
  
• Elevated Walkways and Railings
  
  
• Water Treatment Plants
  
  
• Foundations and Anchor Systems
  

Any time you're bolting together structural steel in an outdoor setting, HDG is the smart choice.

Understanding Thread Tapping: tZn vs. fZn

One important detail with HDG fasteners is the thread fit. Because the zinc coating adds significant thickness, HDG fasteners must be specially tapped to accommodate this:

• tZn (Tapped Undersized): Threads are cut smaller before coating so that after galvanizing, they return to standard dimensions. This ensures proper fit and thread engagement.
  
  
• fZn (Tapped Oversized): Threads are left standard and then galvanized, resulting in a slightly oversized thread. These may not work in assemblies expecting standard tolerances.

At Eurolink, we stock tZn HDG bolts to ensure seamless integration into your assemblies, especially when replacing zinc-plated fasteners or meeting tight mechanical requirements.

What Makes Eurolink Different For Fastener Procurement?

At Eurolink, we don’t just carry HDG bolts…we understand how, where, and why they’re used.

Here’s what sets us apart:

• In-Stock Inventory: Extensive inventory from M12 to M30, with matching nuts and washers (HV sets)
  
  
• Material Test Reports: Available for all structural fasteners
  
  
• European Sourcing Network: If we don’t have it in stock, we’ll get it to you FAST, FASTER, or FASTEST.
  
  
• Expert Support: We help engineers and buyers select the right finish, thread type, and strength grade for their application
  
  
• No Gimmicks, Just Experience: We’ve been specializing in metric fasteners for over 25 years. If it’s metric, we’ve seen it.

Product Availability Snapshot

From the line card, here are some commonly stocked sizes (in millimeters):

• Diameters: M12, M16, M20, M22, M24, M27, M30
  
  
• Lengths: 30 mm to 160 mm
  
  
• Standards: EN 14399-4 bolts, 14399-5 nuts, 14399-6 washers
  
  
• Finishes: Hot Dip Galvanized (standard), Plain Finish (on request)

View our full line card or contact our team for a complete list of in-stock items.

When You Need Strength + Corrosion Resistance, HDG Delivers

Hot dip galvanized structural fasteners are the workhorses behind bridges, buildings, and infrastructure around the world. With the mechanical strength of Class 10.9 steel and a corrosion-resistant coating that stands the test of time, they’re the clear choice for outdoor structural connections.

Eurolink Fastener Supply Service is your trusted source for these metric fasteners, whether you’re sourcing 100 bolts or 100,000.

Have Questions or Need a Quote?

Contact the Eurolink team today.