Hebei Kappa Metal Products Co., Ltd. is one of the most reliable manufacturers and suppliers of hot dip galvanized hex bolt grade 8.8 / 10.9 heavy duty carbon steel hex head bolt in China. Welcome to buy bulk high quality hot dip galvanized hex bolt grade 8.8 / 10.9 heavy duty carbon steel hex head bolt made in China here from our factory. If you have any enquiry about cooperation, please feel free to email us.
Hot Dip Galvanized Hex Bolt HDG Hex Head Bolt Heavy Zinc Coating – 50–100μm Grade 8.8 10.9 Carbon Steel For Outdoor & Marine Applications
The Hot Dip Galvanized (HDG) Hex Bolt is a carbon steel hexagon head bolt coated with a thick, durable zinc layer through the hot dip galvanizing process. Unlike electroplated zinc (blue/yellow), HDG provides superior corrosion resistance for fasteners exposed to harsh environments – including salt spray, moisture, underground, and underwater conditions. It is the standard choice for infrastructure, energy, and marine projects where long service life is required.
Standards: ISO 1461, ASTM A153 (USA), BS 729 (UK), GB/T 13912
Coating thickness: Typically 50–100 μm (depends on bolt diameter and immersion time)
Salt spray test (NSS): >=500 hours (up to 1000+ hours for optimal coating)
Appearance: Matte grey to silver-grey. May have slight roughness or drip marks – these are normal for HDG.
A: HDG coating is 5–10x thicker (50–100μm vs. 5–12μm) and forms a metallurgical bond. It provides 20–50 years of outdoor protection, while electroplated lasts 1–5 years. HDG has a matte grey appearance; electroplated is shiny.
A: Yes. HDG bolts have thicker threads, requiring oversized HDG nuts (tapped to 6AZ/6a tolerance). We supply matching nuts.
A: Minimum 500 hours to red rust, typically 800–1000+ hours depending on coating thickness and bolt size.
Q: Can I use Grade 10.9 for HDG?
A: Yes, but special care is required to avoid hydrogen embrittlement. We perform post-galvanizing baking and process control to ensure safety.
A: In extreme environments (seawater immersion, acid soil), HDG will eventually corrode, but at a rate of ~1μm per year – meaning 50–100 years of protection.
A: Yes – that's why we use oversized nuts. We also perform thread chasing after galvanizing to clean excess zinc from threads.
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