What Is FRP Grating? Materials, Manufacturing and Why It Doesn't Rust

FRP (fiberglass reinforced plastic, also called GRP) grating is a structural panel made of two materials acting together: glass fibers provide strength, and thermosetting resin provides shape and chemical resistance. Neither material is new — the engineering is in how they are combined.

The two ingredients

Glass fibers carry the load. Continuous glass rovings are drawn into the panel in precise amounts — typically 25–35 % of the panel weight — oriented along the directions that must bear load. Glass is stronger than most steel grades by weight and, critically, it does not corrode.

Resin is the matrix that holds the fibers in position, transfers load between them, and forms the surface that touches your chemicals. This is why resin selection (ortho, ISO polyester, vinyl ester, phenolic) matters more than anything else for service life — the resin is the corrosion barrier, and unlike a coating, it is the full panel thickness.

How panels are made

Molded grating: continuous rovings are laid in alternating layers in a heated mold, wetted with resin, and compacted under pressure until cured. The result is a one-piece panel with interwoven strength in both directions — you can cut it anywhere without it falling apart, because the glass is continuous in every direction.

Pultruded grating: fibers are pulled through a heated die that shapes and cures them into profiles — I-bars and rods. The profiles are assembled into panels. Because the glass runs continuously down the bar, pultruded panels are stiffer along the span (about 30 % at equal depth), but the bars must span the supports — strength is directional by design.

Why it cannot rust

Corrosion is an electrochemical process that requires a metal. FRP contains no metal (fixings excepted, which we supply in 316 stainless), so there is nothing to oxidize. A steel panel resists corrosion with a coating that sits on top of the metal; an FRP panel resists it with material that is the same all the way through. Scratch it, cut it, drill it — the exposed surface is the same corrosion-proof composite. That single difference is why the maintenance line for FRP walkways is inspection, not recoating.