In short: Choose 316 stainless steel grating where the floor must be non-combustible, very stiff, or hot. Choose FRP grating where warm chloride water, acids or alkalis attack metal, where the floor must be non-conductive, or where panels must be lifted by hand. Compare both on whole-life cost, using the same span, load and chemical data.
Stainless steel is often the first upgrade buyers consider when galvanized carbon steel grating rusts out. FRP (fiber-reinforced plastic, also called GRP) is the other common option. Both resist corrosion far better than carbon steel, but they fail in different ways and suit different places. This guide compares them factor by factor so you can choose, then quote both on the same basis.
How each material handles corrosion
Type 316 stainless steel resists general corrosion well because of its chromium-rich passive film and its molybdenum content. Its weak points are local: in warm, stagnant chloride service and in crevices such as under clips, bearing-bar joints and deposits, 316 can suffer pitting and crevice corrosion. These sites are typical of seawater splash zones, wastewater plants and chemical areas that are washed down with chloride-bearing water.
FRP grating does not rust or pit. Its corrosion resistance comes from the resin that surrounds the glass fibers, so the question is whether the resin suits the chemical and temperature. Isophthalic polyester, vinyl ester and phenolic resins each have different limits; see polyester vs vinyl ester vs phenolic resin and the FRP chemical resistance guide.
Weight and handling
FRP grating weighs roughly one quarter to one half as much as steel grating of a similar duty. That matters on retrofits: panels can often be carried and placed by two people without a crane, and the load on old supporting steel is lower. Stainless panels of the same size usually need lifting gear. For typical molded panel weights, see FRP grating weight guide.
Stiffness, load and span
Stainless steel is much stiffer than FRP. With FRP, the deflection limit, not breaking strength, usually decides the depth and span. Many specifications use a limit such as span/200 or a fixed millimeter value; BS 4592-0 uses 10 mm or span/200. Read the manufacturer's load table for the exact panel quoted, as explained in how to read FRP grating span and load tables. If a stainless design uses wide support spacing, the FRP alternative may need deeper grating or extra supports.
Fire and heat
Stainless steel is non-combustible. FRP is a combustible material, even when it is made with fire-retardant resin. Where a project or authority requires a non-combustible floor, stainless (or another metal) is the default choice. Where FRP is allowed, ask for the fire test your project names, for example ASTM E84 flame spread, and use phenolic resin where low smoke is needed. See FRP grating fire rating (ASTM E84) and phenolic FRP grating for low smoke.
Electrical behavior
FRP is non-conductive, which suits substations, cable areas and electrolysis plants. Stainless steel conducts and must be bonded and earthed like any metal walkway. If static build-up is a concern in a hazardous area, a standard FRP panel may need an anti-static version; ask for an anti-static grade and its test report.
Key parameters at a glance
| Factor | FRP / GRP grating | 316 stainless steel grating |
|---|---|---|
| Chloride corrosion | No pitting or crevice corrosion | Pitting and crevice corrosion possible in warm, stagnant chloride service |
| Acids and alkalis | Depends on resin; choose from resin guide | Depends on chemical; some acids attack stainless |
| Weight | About 1/4 to 1/2 of steel | Heavy |
| Stiffness | Lower; deflection governs | High |
| Fire | Combustible; fire-retardant and phenolic grades | Non-combustible |
| Electrical | Non-conductive | Conductive; bond and earth |
| Cutting on site | Diamond or carbide blade; seal cut edges | Metal cutting; hot work permit may apply |
| Sources | CSSP; resin guides; BS 4592-0 | CSSP |
Cost: compare whole-life, not price per square meter
Supply price per square meter is only part of the cost. Add freight, installation labor and lifting, the cost of hot-work permits, expected maintenance and the replacement interval. Prices vary widely with resin, depth, surface and quantity, so FIBROVX does not publish a fixed ratio between FRP and stainless prices. For a worked approach, see FRP vs steel grating total cost of ownership and FRP vs steel grating price per m².
Where each one usually wins
Stainless steel is usually better for
- Floors that must be non-combustible by code or client rule
- High-temperature areas near furnaces, flare decks or hot process lines
- Heavy wheeled or point loads with wide support spacing
- Hygienic areas where the client specifies stainless
FRP is usually better for
- Wastewater, seawater splash and chloride washdown areas
- Acid and alkali process areas, with the right resin
- Electrical areas where a non-conductive floor helps safety
- Retrofits where panels must be lifted by hand or the old steel cannot carry more weight
How to get comparable quotes
Send the same data to both suppliers: clear span and bearing-bar direction, uniform and concentrated loads, deflection limit, chemicals with concentration and temperature, fire requirement, panel sizes and cut-outs, and the fixing method. Ask FRP suppliers for the load table and test reports for the exact product. Our FRP grating RFQ checklist lists every field.
Ready to quote? FIBROVX manufactures FRP products in our own factory in China and builds every item to order: sizes, resin system, color, molds and OEM branding. Send drawings, cut lists and duty data to FIBROVX. Trade terms default to CIF destination port; FOB China port is available on request.
FAQ
Is FRP grating stronger than stainless steel?
Not in stiffness. Stainless is much stiffer, so FRP designs are usually governed by the deflection limit and may need deeper panels or closer supports.
Does 316 stainless corrode?
It resists general corrosion, but in warm, stagnant chloride service and in crevices it can suffer pitting and crevice corrosion.
Is FRP grating fire-proof?
No. FRP is combustible. Fire-retardant and phenolic grades reduce flame spread and smoke; ask for the fire test your project requires.
How much lighter is FRP than steel grating?
Typically about one quarter to one half of the weight of steel grating, depending on the products compared.
Which is cheaper?
It depends on resin, depth, size and quantity. Compare whole-life cost, including installation and replacement, using quotes on the same data.
Related guides
Sources
- A Chinese manufacturer, 316 stainless steel grating in marine, chemical and wastewater service
- BSI, BS 4592-0:2006 Industrial type flooring and stair treads — Common design requirements; BS 4592-4:2006 (GRP open bar gratings); BS 4592-6:2008 (GRP molded open mesh gratings), https://knowledge.bsigroup.com
- A resin manufacturer, epoxy vinyl ester resins chemical resistance and resin selection guide
- International Chamber of Commerce, Incoterms® 2020 rules, https://iccwbo.org/business-solutions/incoterms-rules/incoterms-2020/