What this industry manufactures
Gelcoat finishes the exterior, weather-facing surface of FRP water tanks — sectional panel tanks, one-piece cylindrical or rectangular tanks, and underground or overhead storage tanks — applied to the mould before the structural laminate that forms the tank wall is built up behind it.
Why GP Gelcoat Resin is suitable
GP Gelcoat Resin's thixotropic body suits the flat and curved exterior mould surfaces used in tank panel and shell production, and it is not the structural material of the tank wall: glass fibre reinforcement wet out with GP Clear Resin forms the actual structural laminate behind it. One important limitation for this specific application: independent industry sources describe UV-stabilised gelcoat as essential for tank exteriors that stay outdoors for the tank's full service life, since unstabilised polyester can yellow, chalk and eventually degrade under years of continuous sun exposure. GP Gelcoat Resin has no UV-stabiliser package confirmed in its specification, so for tanks expected to hold their exterior appearance over a long outdoor service life, discuss UV-stabilised formulation requirements with our technical team before specifying. This page covers exterior finishing only — it does not apply to interior, potable-water-contact surfaces.
Required resin characteristics
- 01Thixotropic body suited to flat and curved tank panel or shell exterior moulds
- 02High gloss, smooth cured finish for the tank's visible exterior surface
- 03Pigmentable for coloured or branded tank exteriors
- 04Room-temperature MEKP cure compatible with standard tank panel production
- 05Not certified or recommended for interior, potable-water-contact surfaces
Manufacturing process
Gelcoat is sprayed or brushed onto the exterior-facing side of the tank panel or shell mould first and left to gel, then glass fibre reinforcement wet out with GP Clear Resin, catalysed with an MEKP hardener and cobalt octoate accelerator, is built up behind it to form the structural tank wall. Once cured, panels are released from the mould, trimmed, and — for sectional tanks — bolted together on site, with the gelcoat forming the tank's finished exterior surface. The interior surface of a tank is a separate specification question entirely, particularly for potable water storage.
Advantages
- Clean, glossy exterior finish straight from the mould, without post-finishing
- Pigmentable for coloured or company-branded tank exteriors
- Thixotropic body suited to flat and curved exterior panel moulds
- Consistent MEKP/cobalt cure across repeated panel production runs
Common products produced
- Sectional panel water tank exteriors
- One-piece cylindrical and rectangular tank exteriors
- Underground and overhead tank exterior surfaces
Frequently asked questions
No. This page and GP Gelcoat Resin cover exterior tank finishing only. Potable water tank interiors require certified food-grade, NSF/ANSI 61-type materials that Samrat Poly Resins does not currently supply — always confirm interior tank materials meet the relevant drinking-water standards for your project with a certified supplier.
No. It is the cosmetic exterior surface coating, applied to the mould first. The structural laminate that actually forms the tank wall — typically GP Clear Resin reinforced with glass fibre — is built up behind it.
Not as a confirmed feature of its current specification. Since tank exteriors are outdoors for the tank's entire service life, this matters more here than in most other gelcoat applications — for tanks needing long-term outdoor colour and surface stability, discuss UV-stabilised formulation options with our technical team before specifying.
Yes. GP Gelcoat Resin is supplied plain white, and FRP Polyester Pigment can be blended in before catalysing for a coloured or branded tank exterior.
Typically E-glass chopped strand mat, sometimes combined with woven roving for added strength, wet out with GP Clear Resin to form the structural laminate behind the gelcoat.
Need gelcoat for your water tank exterior production?
Get a bulk quote or talk to our technical team about the right gelcoat and laminate combination for your tank panels.