The resin is the first line of chemical defence

Glass fibre provides strength, while the resin matrix protects the fibre and transfers load into it. The fibre itself has low chemical resistance and wicks liquid along its length; choose the wrong resin and even a thick panel will fail from the matrix outward.

So "FRP is corrosion resistant" is not a conclusion that stands on its own. You have to state the medium, concentration, temperature and whether exposure alternates before deciding which resin system fits.

Four resin families, starting with the duty

Our specification table lists four families. Orthophthalic OFR-25 has an oxygen index of at least 28 and is used in general acid and alkali service; OCR is also orthophthalic and is used where fire retardance is not required. Isophthalic IFR-25 has an oxygen index of at least 28 for general industrial service; IFGR-30 is a food-grade isophthalic with an oxygen index of 26 for food processing areas.

Vinyl ester comes in two grades: VEFR-25 has an oxygen index of at least 28 for strong acid and alkali service, while VEFR-10 has an oxygen index of at least 35 and combines higher fire retardance with chemical resistance. Phenolic MP-5 has an oxygen index of about 80 for the highest fire retardance and low smoke.

Choose by medium

For medium-concentration inorganic acids and salts, isophthalic is usually the starting point; for general acid and alkali service, orthophthalic can be sufficient. For strong acids, strong alkalis and some oxidising media, choose vinyl ester, which has the broader resistance range.

For food processing, choose food-grade isophthalic IFGR-30; for the highest fire retardance and low smoke, choose phenolic MP-5; where fire retardance and aggressive chemical exposure coincide, look at a higher-oxygen-index vinyl ester such as VEFR-10. Fire performance and chemical resistance are separate dimensions; one cannot substitute for the other.

Concentration, temperature and alternating exposure

The same resin behaves differently at different concentrations and temperatures. Dilute acid and concentrated acid, ambient and elevated temperature, continuous immersion and occasional splash cannot share one conclusion. Cleaning agents, steam, disinfectants and alternating exposure are part of the duty and must be stated.

Long-term service temperature is generally kept below the resin's heat-distortion temperature minus a safety margin. Near the upper limit, choose a higher-temperature grade and leave a corrosion allowance. Do not rely on the resin name alone, or on a single ambient-temperature immersion datum.

Structure, edge sealing and load matter too

Resin answers what the panel resists; structure and load answer what it can carry. Panel depth, mesh and support span come from the load and deflection tables; the best resin will still deflect or fail if the span is too long.

Cutting and drilling expose glass fibre, so the cut must be sealed with the same resin family as the panel. Otherwise the medium travels along the fibres from the cut and the panel delaminates from inside. In chemical service, a general-purpose sealant is not a substitute for resin sealing.

What to give the supplier

Provide a medium list: each chemical, its concentration, temperature, contact time, whether exposure alternates, and the cleaning and disinfection method. Then give the load, span, fire rating, food-grade requirement and installation environment.

Do not write only "acid and alkali resistant" or "corrosion resistant". The same phrase can point to completely different resins at different concentrations and temperatures. Where possible, ask for a case in the same duty or an immersion sample, and request resin content, Barcol hardness, flexural strength, fire test and load-deflection reports.

Join the selection together

Resin systems are listed in the FRP grating specifications guide; medium and duty guidance is in the chemical-resistant grating guide. Load and span must come from the load tables and cannot be inferred from the resin grade.

Edge sealing is covered in the FRP grating fabrication guide; span and deflection in the FRP grating load capacity guide

The short rule

List the medium, concentration, temperature and exposure first, then choose the resin family. Fire performance, food grade and load capacity are three separate gates, and none of them can be replaced by the words corrosion resistant.