FRP Grating for Water Treatment: Corrosion Resistance, Non-Conductive Flooring, and 50-Year Maintenance-Free Design Life
Steel grating in water treatment works. Until it doesn't. Chlorine attacks it from above. Hydrogen sulphide attacks it from below. Every few years, the platform is taken out of service, scaffolded, and repainted at cost to the operator. FRP grating eliminates that maintenance cycle entirely, and it does so while being 75% lighter, non-conductive, and resistant to the full chemical range that water treatment and wastewater infrastructure produces. For AMP8 asset owners specifying secondary access structures across a 50-year horizon, FRP grating is not the premium option. It is the lower whole-life cost option.
Published by Reinforce Technology | 5 October 2026
Water treatment and wastewater infrastructure places unusual demands on secondary access structures. Walkways, platforms, and trench covers sit in environments that combine continuous moisture, free chlorine from dosing operations, hydrogen sulphide gas generated by anaerobic processes in wastewater, and the mechanical traffic of operators carrying out routine inspection and maintenance. Steel grating is the traditional specification for these platforms. It is also the specification that requires the most ongoing maintenance, generates the most safety incidents in confined chemical environments, and imposes the highest structural dead load on the assets it is mounted to. FRP moulded grating addresses all three of these problems without compromising on load capacity for standard access platform service (Treadwell Group, 2025).
The Corrosion Problem Steel Grating Cannot Solve
Free chlorine, used across potable water treatment for disinfection, is corrosive to carbon steel and attacks the zinc coating of galvanised steel over time, accelerating where moisture collects in the grating mesh. In wastewater treatment, the problem is compounded by hydrogen sulphide. H2S is generated wherever anaerobic bacterial activity occurs in sewage, particularly in enclosed sumps, wet wells, pump stations, and covered sewer channels. It attacks steel from the underside of access platforms through continuous gas phase exposure, causing uniform section loss in structural members that may not be visible from above until the structure has already degraded (UKWIR, 2023).
The consequence for operators is not just corrosion. It is a maintenance schedule: periodic inspection, surface preparation, and recoating of steel grating platforms in environments where the chemical exposure that caused the corrosion continues during the maintenance operation. That maintenance requires personnel to work on or adjacent to the corroded structure in wet, chemically active conditions. FRP moulded grating in vinyl ester resin is resistant to both free chlorine and H2S at the concentrations present in water treatment and wastewater environments, and it does not corrode. There is no coating to maintain. There is no recoating schedule. There is no maintenance campaign driven by surface condition (IntechOpen, 2022).
Non-Conductive in Wet Electrical Environments
Water treatment sites run significant electrical infrastructure at close proximity to wet process areas. Dosing pumps, UV disinfection banks, flow meters, and control panels are located on or adjacent to the access platforms that FRP grating forms. Steel grating in these environments is electrically conductive and requires earthing and bonding to the site electrical system. FRP grating is a non-conductor. It does not require earthing, does not create stray current paths, and does not contribute to the galvanic corrosion that results where dissimilar metals meet in wet conditions. On platforms adjacent to UV equipment or chemical dosing points, the elimination of conductive flooring removes one category of electrical risk from the access structure entirely.
Weight and Dead Load on Tank Covers and Suspended Platforms
Many water treatment platforms are suspended over tanks, mounted on cantilever brackets from tank walls, or supported on secondary steelwork spanning between primary structural members. Every kilogram of dead load in the grating is a kilogram of load that the supporting structure must carry in addition to the live load of operators and equipment. FRP moulded grating at 38x38mm mesh in standard depths is approximately 75% lighter than steel grating of equivalent depth. On a platform spanning a clarifier or a filter bed, that weight reduction translates directly into reduced section size requirements for the supporting steelwork, or increased capacity for the existing structure where grating is being replaced on a refurbishment project. For operators replacing corroded steel grating on AMP8 asset refurbishment programmes, lightweight FRP replacement panels can frequently be installed without structural upgrade to the existing supports (Ofwat, 2024).
Anti-Slip Performance in Wet Conditions
Water treatment walkways are wet. Operators traverse them carrying tools and equipment in conditions that include spray, overflow, and general process moisture. The standard specification for FRP grating in these environments is gritted top surface, in which an abrasive layer of aluminium oxide or silicon carbide aggregate is bonded to the top face of the grating during manufacture. Gritted FRP grating maintains high slip resistance even when wet, oily, or contaminated with process chemicals, meeting the anti-slip performance requirements of access platforms in UK water infrastructure without additional surface treatment or maintenance to maintain grip (Health and Safety Executive, 2022).
Applications in Water Treatment and Wastewater
FRP moulded grating at 38x38mm mesh with gritted anti-slip top surface is the standard specification for walkways and inspection platforms over clarifiers, filter beds, settlement tanks, aeration lanes, and chemical dosing areas. At 50x50mm open mesh, FRP grating is used for drainage channels and trench covers where maximum open area for drainage is required alongside corrosion resistance to the process chemistry below. In enclosed wastewater structures including wet wells and pump stations, where H2S concentrations are highest and access is most constrained, the non-sparking cutting and installation properties of FRP grating are an additional safety property, removing the ignition risk from installation and maintenance work in potentially flammable atmospheres.
FRP moulded grating delivers what steel grating cannot in water treatment and wastewater environments: corrosion resistance to the full chemical range of the process, non-conductive flooring in wet electrical areas, 75% dead load reduction on tank covers and suspended platforms, and a 50-year maintenance-free design life. For AMP8 new-build and refurbishment projects specifying secondary access across water infrastructure assets, FRP grating is the material that reduces whole-life cost, reduces maintenance intervention, and removes the corrosion risk from the access structure for the life of the asset. Contact Reinforce Technology to discuss specification for your project.
FRP grating load ratings and chemical resistance depend on panel type, resin system, mesh size, depth, span, and support configuration. Specification should be confirmed against the structural and chemical conditions of the specific installation.
References
Health and Safety Executive (2022) Slips and Trips: Guidance for Employers on Identifying Hazards and Controlling Risks. HSE Books, London. Available at: https://www.hse.gov.uk/pubns/hsg155.htm [Accessed: 5 October 2026]. [Anti-slip flooring requirements for wet industrial environments; gritted surface treatment for walkways subject to process moisture and chemical contamination].
IntechOpen (2022) 'Fibre-Reinforced Polymer (FRP) in Civil Engineering', in IntechOpen Engineering Series. Available at: https://www.intechopen.com/chapters/84203 [Accessed: 5 October 2026]. [Vinyl ester resin FRP grating corrosion resistance to free chlorine and H2S at water treatment concentrations; no maintenance recoating; 50-year design life in corrosive process environments].
Ofwat (2024) AMP8 Price Review Final Determinations. Available at: https://www.ofwat.gov.uk/regulated-companies/price-review/2024-price-review [Accessed: 5 October 2026]. [£104bn AMP8 investment 2025 to 2030 across UK water infrastructure; refurbishment and new-build programmes across treatment works, pumping stations, and network assets].
Treadwell Group (2025) FRP Grating for Water and Wastewater Treatment Infrastructure. Available at: https://www.treadwellgroup.com.au/frp-grating-water-treatment [Accessed: 5 October 2026]. [Moulded FRP grating standard specification for water treatment walkway and platform applications; corrosion resistance to free chlorine and H2S; 50-year maintenance-free design life; non-conductive in wet electrical environments].
UKWIR (2023) Corrosion of Infrastructure in Wastewater Environments (IGN 4-25-02). UK Water Industry Research, London. [H2S attack on steel structures in wastewater environments; section loss in enclosed spaces; replacement cycle costs for galvanised and mild steel secondary access structures in pump stations and wet wells].
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