Three corrosion zones in a port

The corrosion environment for port grating splits into three zones: the salt spray zone above deck, the tidal and splash zone, and the submerged or wet-dry zone below. Oxygen, humidity, chloride concentration and temperature differ between them, so the grating and its fixings are selected separately.

The salt spray zone is dominated by thin liquid films and salt crystals, and its corrosion rate follows humidity and wind direction; the splash zone has plenty of oxygen and frequent wet-dry cycling and is the harshest position; the submerged zone is low in oxygen, but marine growth and current scour bring a different set of problems.

Grating is used mainly on deck, jetties, mooring platforms and cargo handling areas. Two positions a few tens of metres apart can differ greatly in service life, so the specification is divided by zone rather than written once for the whole quay.

Salt spray and the tidal zone

Salt spray crystallises on the face and the underside of the grating, and the crystals absorb moisture to form a permanently damp film. The resin surface chalks gradually in that environment, and fasteners and supports usually corrode before the panel itself.

Supports in the tidal zone are immersed and exposed as the tide moves. Wet-dry cycling concentrates chloride in crevices, and carbon steel brackets are consumed quickly even when galvanized; supports and fixings must be selected for the splash zone, not copied from the deck.

Cut edges, drilled holes and worn spots are the entry points for corrosion. Edge sealing must be complete before installation, and site cuts need a fresh coat of edge resin; exposed fibre at a cut draws water in like a wick and corrosion starts inside.

Marine projects offer useful corrosion experience, summarised under FRP grating for marine environments

UV and ageing

A port has no shade, so the grating takes UV for years. Resin chalking and fading are normal ageing, but the chalked layer hides cracks and exposed fibre, so clean before inspection and do not judge life from colour alone.

UV ageing runs at different rates on the sunny and shaded faces, and one batch can show a clear colour difference. The difference does not affect capacity, but it affects appearance acceptance; where colour matters, state the permitted range and the acceptance condition in the contract.

UV absorbers and a surface veil slow ageing but cannot stop it. For a long design life, put surface inspection and local repair into the maintenance plan rather than waiting for exposed fibre.

Wave, wind and berthing loads

Grating on jetties and mooring platforms takes wind load, wave impact and vibration from berthing. Fixings cannot be chosen from panel weight alone; they are checked against wind uplift, splash and maintenance load together, and edge panels are the first to lift.

Berthing load passes through fenders and bollards, and the grating platform does not take the ship impact directly, but vibration and displacement reach the fixings. Clips must resist loosening, hold-down plates need enough clamping force, and friction alone is not a fixing under long-term vibration.

Jetty walkways also carry people and equipment. Pipes, tools and equipment may be stacked during maintenance, so the load table is read for the actual case rather than pedestrian uniform load alone.

Vehicle and trolley loads

Forklifts, tractors and trolleys run on the deck. FRP grating has limited concentrated load capacity, and forklift tyre contact pressure produces high local stress; traffic areas should normally use steel grating or concrete, with FRP kept for foot traffic and light trolleys.

Trolley and pallet wheels wear the surface, and grit loses grip once worn. Busy routes need a wear-resistant surface and deeper bearing bars, with protection plates at corners and loading points.

Vehicle load also brings horizontal force from braking and turning. Fixings must take that thrust, with closer spacing at edges and corners, not just self-weight and a few clips.

Fixings and supports

Port grating usually sits on steel or concrete beams and is fixed with stainless clips, hold-down plates and bolts. The support surface must be level, because unevenness loads the panel locally; packers must be corrosion resistant, not ordinary steel shims.

Long walkways need expansion joints, fixed at one end and sliding at the other. Quay structures move and settle more than factory buildings, and grating locked on four edges will crack at the joints and shear its fasteners.

Support spacing comes from the load table, and edge support must be continuous. A cantilevered panel edge deflects, feels loose and puts extra bending on the fixings, as set out in FRP grating fasteners and installation

Walkway continuity and safety detail

Deck walkways must be continuous, with no step between grating, concrete, steel platforms and stairs. A step is a trip hazard and a water trap; transition supports and banding level the junction, the fall follows the drainage requirement, and the overall platform layout is covered under industrial work platform solutions

Openings and holes in the grating need covers or guardrails. Cable trenches, valve pits and survey holes often sit in the middle of a deck walkway, so covers must be flush, securely fixed and unable to be lifted by a vehicle wheel.

Slip resistance is selected separately for wet and oily zones. Clean water on the deck is usually handled by a concave surface, while fuelling, workshop and loading areas carry oil and need grit, as described under anti-slip FRP grating practice

Inspection and replacement planning

Port grating inspection is graded by zone: every six months in the splash zone and on mooring platforms, annually on the deck, every two years on dry routes. The check covers cracks, whitening, exposed fibre, grit wear, fastener corrosion and support distortion.

Replacement should fit the quay maintenance plan. The panels are light and a single panel needs no heavy plant, but mixing old and new brings colour difference, thickness difference and joint steps; a shutdown replacement keeps appearance and fixing detail consistent.

Before replacement, confirm the resin system, depth and bar spacing of the original. Port conditions may have changed, for example with new washdown or chemicals, so the new specification is checked against the current duty rather than copied from the old order.

Selection points

The inquiry should state the position, corrosion zone, load, slip requirement, fixing method and colour. Saying quay grating alone leaves the supplier unable to choose resin or surface, and the quotation defaults to a standard product.

Resin follows salt spray and UV, fasteners follow the splash zone, and supports follow load and movement. The three are settled together, not by choosing the grating and adding fixings later.

The delivery state must cover banding, openings, edge sealing and matching fasteners. Site fabrication is limited at a port, so the more is finished in the factory, the less dust and rework on site.

• Write a separate specification for each corrosion zone.
• Do not use FRP grating in vehicle traffic areas.
• Leave expansion joints with one sliding end on long walkways.
• Supply banding, openings and fasteners as a matched set.