GRP Grating vs. Stainless Steel: When is the Surcharge Worthwhile? | Formavit
Material Knowledge

GRP Grating vs. Stainless Steel: When is the Surcharge Worthwhile?

approx. 6 minutes reading time
Stainless steel is considered the premium material par excellence: rust-free, durable, visually appealing. GRP is lighter, corrosion-resistant, and costs less to purchase. But which one is really better in practice? This article objectively compares both materials, identifies the differences between stainless steel grades V2A and V4A, and shows when GRP is the smarter choice.

What is stainless steel as a grating material?

Stainless steel is not a single material, but a group of corrosion-resistant steel alloys with at least 10.5% chromium content. In practice, two grades are used for gratings:

1.4301 (V2A) is the standard stainless steel. It contains chromium and nickel, is well suited for normal outdoor and indoor applications, and is corrosion-resistant to atmospheric influences and weak chemicals. However, in chloride environments such as swimming pools or near the sea, it is susceptible to pitting corrosion.

1.4404 (V4A) additionally contains 2 to 2.5% molybdenum. This addition significantly improves resistance to chlorides and aggressive acids. V4A is the preferred material in the food industry, in swimming pools, and in chemical process engineering.

Important: Not every stainless steel is suitable for every application. Installing V2A in a chloride environment is a common planning error that leads to premature failure.

What is GRP?

GRP stands for glass fibre reinforced plastic. GRP gratings consist of a resin-glass fibre matrix and are manufactured from isophthalic resin, vinylester or phenolic resin depending on the requirement. Vinylester-GRP achieves a chemical resistance that is comparable to or superior to V4A in many areas.

GRP does not rust, does not conduct electricity and weighs about 40 to 50% less than a comparable stainless steel grating. The surface is standard anti-slip R13 V10 according to DIN 51130, putting it in a class that stainless steel only achieves with complex processing.

Standard basis: GRP gratings according to DIN 24537-3, anti-slip R13 V10 according to DIN 51130, fire behaviour Bfl-s1 according to EN 13501-1.

The direct comparison: GRP vs. Stainless Steel

Material comparison at a glance

GRP Grating Stainless Steel V2A (1.4301) Stainless Steel V4A (1.4404)
Corrosion Resistance Complete, permanent Good, not chloride-resistant Very good, also chlorides
Saltwater and Chlorine Fully suitable Not suitable Suitable
Weight 10 to 14 kg/m² 20 to 35 kg/m² 20 to 35 kg/m²
Electrical Conductivity Non-conductive Conductive, earthing required Conductive, earthing required
Slip Resistance R13 V10 according to DIN 51130 Depends on surface Depends on surface
Hygiene / FDA Conditionally suitable Yes, with suitable grade Yes, standard-compliant
Appearance in visible areas Industrial High-quality, architectural High-quality, architectural
Maintenance Effort None Low Low
Acquisition Costs Medium High Very high
TCO over 15 years Favorable Medium High

Corrosion: Where both materials stand

At first glance, stainless steel and GRP seem to be equally well positioned. Neither rusts in the classic sense. The decisive difference, however, lies in the details.

V2A (1.4301) is suitable for normal outdoor atmospheres and weakly aggressive media. As soon as chlorides come into play, i.e. in swimming pools, near the sea, on offshore facilities or in chlorine-containing cleaning processes, pitting corrosion occurs. This begins invisibly below the surface and often only becomes noticeable after years through structural damage.

V4A (1.4404) with added molybdenum withstands chloride environments significantly better. However, it is not indefinitely resistant. At very low pH values, for example in sulfuric acid production or in strongly oxidizing acids, even V4A reaches its limits.

GRP in vinylester version is resistant to a very wide range of chemicals, acids and alkalis, thereby surpassing both V2A and V4A in many chemical process environments. For extreme chemical resistance, consultation based on the specific media is recommended.

Planning note: Using V2A in swimming pools or marine environments is a common and costly mistake. Those who want to save money here should choose either V4A or GRP.

Weight and Installation

Stainless steel has a density of approximately 7.9 kg per liter, while GRP is around 1.8 to 2.0 kg per liter. A stainless steel grating weighs between 20 and 35 kg per square meter depending on the design, while a comparable GRP grating weighs 10 to 14 kg per square meter.

This makes a significant difference for larger areas. Stainless steel gratings generally require lifting equipment or at least two installers for areas of approximately 10 m² or more. GRP can be carried by two people, cut with a circular saw or hand-held circular saw, and installed without special tools.

For hard-to-reach areas such as sewage treatment plants, offshore platforms, roof structures, or basements, GRP is not only the lighter, but often also the more economical choice for installation.

Hygiene and Appearance: The Clear Domain of Stainless Steel

There are areas where stainless steel is irreplaceable. The food industry, large kitchens, pharmaceutical companies, and medical facilities require materials that are normatively and often legally prescribed. Stainless steel 1.4301 or 1.4404 with an electropolished surface is FDA-compliant, easy to clean, and meets the relevant hygiene standards.

GRP is chemically resistant and is used in many industrial sectors, but it does not automatically meet the strict hygiene requirements of these industries. For areas with direct food contact or under ongoing official control, stainless steel is the standard-compliant choice.

Even in visible architectural areas, stainless steel has a clear advantage. Its metallic appearance harmonizes with glass, concrete, and wood and is preferred by planners and architects when the material remains visible, for example, as balcony decking, stair treads, or design elements.

Conclusion on Hygiene and Appearance: Wherever standards prescribe the material or where the material should be visible and representative, stainless steel is the right choice.

Electrical Properties

Stainless steel conducts electricity. This applies to both V2A and V4A. In areas with electrical installations, control cabinets, or busbars, stainless steel must be earthed. This is legally required, incurs installation costs, and requires regular inspections.

GRP is not electrically conductive. No earthing obligation, no inspection intervals, no risk of insulation faults. For installations along railway lines, in substations, in data centres, or in electrical engineering, this is a decisive safety and cost advantage.

Costs: What the comparison really shows

Stainless steel V4A is significantly more expensive to purchase than GRP. V2A is also above the level of GRP, but the difference is smaller. In addition, there are higher installation costs due to the greater weight.

In operation, stainless steel is low-maintenance, but not free of cost. Earthing and electrical inspections are incurred, as are any cleaning costs for higher hygiene requirements. In chloride environments, incorrect material selection risks premature replacement, which negates all acquisition savings.

GRP has no such follow-up costs. Once installed, the material is maintenance-free. In aggressive environments, in new buildings with a long planned service life, and wherever earthing costs and maintenance intervals are factored into the budget, GRP is the more economical option over its lifespan.

Guideline: In hygiene and visible areas, as well as for very high loads, the surcharge for V4A is often justified. In corrosive industrial environments without hygiene requirements, GRP is cheaper over 15 years.

When is which material the right choice?

Stainless steel for

  • food and pharmaceutical areas
  • visible architectural areas
  • very high surface loads
  • welding work and on-site adjustments
  • legally prescribed grades

GRP for

  • aggressive chemicals and acids
  • saltwater and chlorine atmospheres
  • electrical insulation required
  • hard-to-reach areas
  • zero-maintenance over long periods
  • R13 slip resistance as standard

Conclusion

Stainless steel is not a bad material; it is the right material for specific requirements. If you are building in the food industry, designing representative visible areas, or bearing very heavy loads, you cannot avoid stainless steel. And if you choose stainless steel, you should carefully select the grade: V2A in chloride environments is a costly mistake.

For industrial applications in corrosive or chemically aggressive environments, for areas with electrical insulation requirements, and for all projects where installation effort and life cycle costs matter, GRP is the more considered choice. Lighter, maintenance-free, and more economical over its lifespan.

Frequently Asked Questions

That depends on the application. GRP is lighter, electrically insulating, and often more resistant to aggressive chemicals than V2A. Stainless steel V4A is the better choice in hygiene areas such as the food industry and for very high mechanical loads.
Stainless steel contains chromium, nickel, and, in the case of V4A, molybdenum. These alloying elements are expensive, and the processing effort is higher than for normal steel. Additionally, the significantly higher weight increases transportation and installation costs.
For standard applications, 1.4301 (V2A) is sufficient. In chloride-containing environments such as swimming pools, offshore, or the chemical industry, 1.4404 (V4A) with added molybdenum is required. GRP is often the more economical alternative in these environments.
GRP is chemically resistant and is used in many industrial sectors. For areas with strict hygiene and FDA requirements, however, stainless steel 1.4301 or 1.4404 with an electropolished surface is the standard compliant solution.
Stainless steel has a density of around 7.9 kg per liter, while GRP is about 1.8 to 2.0 kg per liter. A stainless steel grating weighs 20 to 35 kg per square meter, depending on the design, while a comparable GRP grating weighs 10 to 14 kg per square meter.

Sources and Standards

DIN EN 10088 (stainless steels), material 1.4301 and 1.4404 according to DIN EN 10088-1, DIN 51130 (slip resistance R13 V10), EN 13501-1 (fire behavior Bfl-s1), DIN 24537-3 (GRP gratings), DIN 24537 (gratings dimensions and loads).