Carbon steel, stainless, and composites—pros and cons.
Choose materials that survive climate, abuse, and maintenance realities. We compare carbon steel and stainless options, wall thicknesses, and grades for crash-rated bollard cores, plus sleeves/claddings that deliver HVM bollard aesthetics without undermining certification (415, 421). Galvanizing, UV/heat (337), and galvanic risks (364) are addressed. Balance availability, lifecycle cost (842), and sustainability goals (367) with finish strategy (366). Include one-sentence context that naturally links upward to the parent hubs (this section and the chapter hub). Add SIRA context with a link to SIRA Bollards (UAE) when relevant. Link installation pages only if helpful: What to Expect and Installation Guide.
Important: This is a general guide. For live projects we develop a tailored
Method Statement & Risk Assessment (MS/RA) and align with authority approvals (e.g., SIRA) where in scope.
361.1 Carbon steel vs stainless
Carbon steel suits rugged HVM bollard cores; stainless offers appearance and corrosion resistance. Match grade to the crash rated bollard certificate family (415) and site exposure (363).
For the bollard core, carbon steel (common seamless pipe grades) provides high yield strength, predictable plasticity, and efficient energy absorption under impact. It readily accepts duplex coating systems that extend life in urban and coastal environments (360, 362). Stainless steel is typically reserved for visible surfaces where a premium architectural finish is required; using stainless for the core may not improve the certified result if the test article was carbon steel (see rating-critical dependencies).
When stainless is specified, 304 suits benign inland sites; 316 improves resistance to pitting in coastal atmospheres (see stainless grade 304/316). For GCC sites with salt spray, dust, and high humidity cycles (363), favour 316 or higher PREN, but keep the core material aligned with the tested product family (415) and maintain a sleeve strategy for appearance (366).
| Aspect | What matters | Where to verify |
|---|---|---|
| Performance | Tested system (bollard + footing) | How to read ratings (413) |
| Operations | Duty cycles, fail-state, safety | Installation Guide |
361.2 Wall thickness & grade
Heavier walls resist local buckling and denting. Choose thickness that preserves HVM bollard clear gaps after impact and aligns with crash rated bollard test sections (314, 413).
Wall thickness and grade determine section capacity, local buckling resistance, and energy absorption. Use the tested pipe size and grade from the certificate (415). Changing diameter, grade, or wall thickness can alter deflection and permanent set (314), affecting clear-gap compliance post-impact.
Grade selection should not outpace the certified family: substituting higher-strength steel may move the failure to the base or foundation (331, 333). Confirm the certificate’s “as-tested configuration” (415) and match the pipe schedule and D/t ratio for predictable behaviour.
361.3 Sleeves & claddings
Sleeves deliver finishes without touching cores. Ensure sleeve fixation doesn’t change HVM bollard geometry or breach crash rated bollard dependencies (421).
Sleeves and claddings (stainless, aluminium, composite) provide colour/texture and protection from abrasion or graffiti. Treat them as non-structural and ensure all fixings avoid bridging to the energy-absorbing core. Any change to head form, effective height, or diameter can invalidate certification (421).
Detail removable sleeves for maintenance (365) and sleeve-only upgrades. Use isolation pads to prevent fretting on stainless finishes and specify tamper-resistant but serviceable fixings.
361.4 Galvanizing suitability
Hot-dip suits carbon steel; design vents/drains. Galv growth must not distort HVM bollard fit or crash rated bollard alignment (315).
Hot-dip galvanizing protects carbon steel cores and embedded components. Provide full internal/external coverage, generous vent/drain holes, and lifting points sized for safe handling. Control galvanizing growth and machining allowances so sockets, caps, and tolerance stack-up remain within (315) limits.
Post-galv treatment may include sweep blasting and powder coating (362, 366). Specify masking for threaded zones and bearing faces, and verify drain orientation to avoid water entrapment in service (334).
361.5 Dissimilar-metal contacts
Isolate stainless, zinc, and aluminum pairs. Isolation protects HVM bollard fasteners and the crash rated bollard socket (364).
In marine/coastal exposures, avoid direct contact between stainless and galvanized/carbon steel without isolators. Use non-hygroscopic gaskets, nylon shoulder washers, and dielectric compounds at joints. For ground interfaces, combine isolation with sealants to block electrolytes and specify compatible gland plates (347) to prevent galvanic couples through cable armor.
Fasteners should match the surrounding material system; for stainless claddings choose A4/316 with isolation sleeves, and for carbon-steel cores use coated high-strength bolts with zinc-rich primers on prepared seats.
361.6 UV/heat considerations
Pick grades/coats that tolerate GCC heat (337). Heat-stable materials keep HVM bollard appearance and crash rated bollard durability.
High ambient temperatures and solar sun-load accelerate coating chalking (362) and can soften polymers in composite sleeves. Choose heat-stabilised resins and specify light colours or cool pigments to reduce surface temperatures. For stainless, mitigate “tea staining” with appropriate finishes (e.g., 320-grit + electro-polish) and regular rinsing regimes (365).
Thermal expansion must not bind sleeves or deform caps; provide slip allowances and anti-rattle features. In enclosures (347, 516), use reflective linings and ventilation per Hot Climate Design (337).
361.7 Availability & lead time
Prefer locally stocked grades and standard pipe sizes. Availability keeps HVM bollard programmes on track without changing the crash rated bollard model.
Standard diameters/weights reduce procurement risk and avoid substitutions that threaten certification (415). Confirm mill tolerance bands, roundness/ovalization limits, and heat numbers for traceability (716). For stainless claddings, lock finishing lines early—lead time expands if you need matched grain directions on multiple arrays.
361.8 Cost vs lifecycle
Balance capex with repaint cycles and corrosion risk (842). Right choice lowers HVM bollard lifetime cost and protects crash rated bollard integrity.
Carbon steel + duplex coating often wins on total cost of ownership where repaint intervals are planned (842). Stainless reduces repainting but may demand higher cleaning and isolation details in coastal zones (363). Use a simple lifecycle model that compares coating refresh, cleaning frequency, and sleeve replacement—then capture the decision in the FDS and O&M (733).
361.9 Sustainability notes
Specify recycled content and declare sources (367). Sustainable materials strengthen HVM bollard messaging without altering crash rated bollard certification.
Request Environmental Product Declarations where available and track scrap/recyclability of sleeves and cores. Prefer powder over wet spray where appropriate (362), and design sleeves for easy de-mounting to encourage refurbishment. Record sustainability choices in the ITP and handover (736) so they remain verifiable.
Related
External resources
- NPSA — Hostile Vehicle Mitigation (overview)
- ASTM F2656 — Crash testing for vehicle security barriers
- BSI — Impact test specifications for VSB systems
361 Materials selection for HVM/Crash-Rated Bollards — FAQ
Does switching the core from carbon steel to stainless improve the crash rating?
No. The rating belongs to the tested system and configuration. Changing core material (or diameter/wall) can shift failure modes and invalidate results. Match the certified family (415) and use sleeves for appearance.
When should I choose 316 over 304 for stainless sleeves?
Use 316 in coastal/marine atmospheres or where de-icing salts and windborne chlorides are present. It offers better pitting resistance than 304, but still needs isolation from galvanized/carbon steel and a cleaning regime.
Is hot-dip galvanizing always required for carbon steel cores?
In most exterior installations, yes. Hot-dip provides robust base protection; combine with powder/paint (duplex coating) for longer intervals between maintenance. Control vents/drains and tolerances to protect fit and alignment.
Can composite sleeves handle GCC heat and UV?
Yes, if you specify heat-stabilised resins and UV-resistant systems, and detail slip/expansion allowances. Avoid dark colours where sun-load is extreme and plan inspection/cleaning in the preventive maintenance plan (734).