Technical guide
Which coating for fasteners?
Zinc plating for dry indoor use. Hot-dip galvanizing for outdoor structural steel – with oversize-tapped nuts. PTFE / Xylan for flange bolting in corrosive process plants, where low, even friction helps. TAKECOAT-1000 where maximum corrosion protection is required: rated for at least 6,000 hours before red rust.
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Short answer
- Zinc plated – thin, cheap, indoor.
- Hot-dip galvanized – thick zinc for outdoor steelwork; nuts tapped oversize.
- PTFE / Xylan – fluoropolymer for process flanges; low friction.
- TAKECOAT-1000 – highest protection; HBS is Europe's only authorized supplier.
- With any coating: use torque values matched to the coating.
Comparison
Six coatings we apply.
| Coating | Process | Best for | Fit and threads | Note |
|---|---|---|---|---|
| Zinc plated | Electroplated zinc (ISO 4042) | Dry indoor, machinery | Thin – standard threads | Hydrogen embrittlement risk on hard parts (> 320 HV, class 10.9 / 12.9) – needs controlled processing |
| Hot-dip galvanized (HDG) | Dipped in molten zinc (ISO 10684) | Outdoor structural steel, towers, civil | Thick – nuts tapped oversize, order as a set | Not for fine threads or small sizes |
| Xylan 1070 / 1424 (PTFE) | Fluoropolymer coating over a pretreatment | Flange bolting in refineries, chemical and offshore | Thin film – standard threads | Low, consistent friction; lower torque needed for the same preload |
| TAKECOAT-1000 | High-performance coating system | Severe corrosion, offshore, long service life | Thin film – standard threads | Rated for at least 6,000 hours before red rust |
| Sherardized | Zinc diffusion coating | Outdoor parts with tight tolerances | Even layer, also in threads | Hard, abrasion-resistant zinc–iron layer |
| Geomet-500 | Zinc-aluminium flake, chromium-free | Automotive-type and high-strength parts | Thin – standard threads | Applied without electroplating |
How to choose
Three questions.
- 01Where does the bolt sit?Indoors and dry: zinc plated or plain. Outdoors on steelwork: hot-dip galvanized. In a process plant with chemicals, salt or condensation: PTFE / Xylan or TAKECOAT-1000.
- 02How hard is the bolt?High-strength bolts (10.9, 12.9 and other parts above 320 HV) are sensitive to hydrogen from electroplating. Choose a non-electrolytic coating such as Geomet, Xylan or TAKECOAT.
- 03How hot does it get?Every coating has a maximum service temperature, often lower than the steel itself. Tell us the design temperature and we will advise the coating.
FAQ
Questions we get every week.
- Do coated bolts need a different torque?
- Yes. Coatings change the friction in thread and under the nut. PTFE / Xylan in particular is slippery, so the same torque gives more preload. Use torque values for the coating or a calibrated method.
- Why must HDG nuts be tapped oversize?
- The galvanized layer on the bolt thread is too thick for a standard nut. ISO 10684 therefore uses oversize-tapped nuts, which is why we supply galvanized bolts and nuts as matched sets.
- What is TAKECOAT-1000?
- A high-performance coating system rated for at least 6,000 hours before red rust. HBS Solutions is Europe's only authorized supplier.
- Can stainless bolts be coated?
- Usually not needed. For galling, a PTFE coating on the nut helps. For cleanrooms we offer EPK treatment instead of a coating.
- Is Xylan the same as PTFE?
- Xylan is a brand of fluoropolymer coatings that contain PTFE. Xylan 1070 and 1424 are the types most used on fasteners.
- Which coating do you recommend for offshore flanges?
- B7 / 2H with PTFE / Xylan or TAKECOAT-1000 – the combination most often requested by our customers.
Next step
Configure, download or ask.
Reviewed October 2026 by HBS Solutions. Based on ISO 4042, ISO 10684 and supplier data for the coatings named. Values are minimums from the standard; always check the edition and options named in your project specification.
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