Steelpaint’s Stelpant PU Combination 500 is a moisture-cured polyurethane coating with micaceous iron oxide, offering strong UV, water, and chemical resistance for steel, metal, and concrete in harsh C5 environments.
Steelpaint has successfully completed its first large-scale industrial trial of Stelpant PU Combination 500 on fibre-reinforced plastic (FRP) and glass flake composite structures, marking a significant breakthrough in protective coatings
technology.
The German manufacturer confirmed the long-term performance of its high-build, one-component coating following a landmark refurbishment project at a major processing and production site in Ban Chang, Thailand. The site’s nine vertical FRP tanks – exposed to constant UV radiation, high humidity, and airborne chemical vapours – were externally coated with Combination 500 in November 2021.
A total of 1,250m² of surface area was treated with a 100μm dry film thickness (DFT) base coat, followed by a further 100μm topcoat
applied by roller. The success of this application led to a further test in March 2025, this time on the 840m² roof of a similar FRP wastewater tank, where a 130μm layer of Combination 500 was finished with a polyurethane topcoat.
“The glass flake matrix had become brittle and porous, compromising the composite’s protective role. Historically, such refurbishment would require a two-component system applied under strict environmental conditions. Instead, our one-component system enabled faster application with only basic surface preparation—just the removal of loose fibre and cleaning using power tools,” has stated Dmitry Gromilin, Steelpaint’s Chief Technical Supervisor.
“By slightly thinning the coating on-site, applicators achieved deep penetration into the fibre matrix, resealing the exposed structure and restoring surface integrity. Combination 500 acts almost like an adhesive—providing mechanical sealing, chemical resistance, and long-term protection in a single layer,” has added Dmitry Gromilin, Steelpaint’s Chief Technical Supervisor.
As a one-component solution, Combination 500 offers both commercial and logistical advantages, particularly for maintenance contractors, by reducing the need for specialised equipment or complex training. The product is fully compliant with ISO 12944 C5 standards and may be combined with Stelpant PU Zinc primer for metallic substrates or a two-component UV-stable topcoat for structures exposed to direct sunlight.
“Combination 500 has already proven its value on hydraulic steel and concrete. This is the first time it has been applied to a glass flake structure in such a harsh setting—and the results speak for themselves. More than three years later, the tanks remain in excellent condition. Conventional coatings often require dry, encapsulated conditions. Our system bypasses those limitations—it applies quickly, adheres well to a variety of surfaces, and cures even in the humid climate typical of Southeast Asia,” has added Frank Müller, Director at Steelpaint.