Thermal insulation coating – Belzona 5871

Belzona 5871 is an epoxy thermal insulation coating providing corrosion protection and cool to touch properties. In this blog, we’ll explain how to


Industries and facilities around the world face challenges linked to the maintenance of pipework, tanks, and vessels. Damage and deterioration of pipes, valves and fittings are a widespread problem; they occur due to corrosion, erosion, thermal cycling, and chemical attack. In order to save energy costs and reduce waste, companies are recognising the importance of insulating and protecting their equipment. However, this creates another problem, corrosion under insulation (CUI). CUI is a major issue which occurs on equipment operating in low, ambient, and high-temperature environments.

Metallic surfaces at ≥ 60°C or < 0°C can cause contact-burn injuries without proper protection

Moreover, equipment operating in low temperatures and sub-zero conditions can experience ice-build-up, condensation and dripping of water. As a result, this can cause slipping hazards and provoke ice burns when handled at < 0°C.

example of Corrosion under insulation (CUI)
Example of corrosion under traditional insulation.

Various solutions are available in the market such as traditional insulation, barriers or guards and water-based coatings. However, individually, they do not hold all the requirements to insulate machinery and equipment whilst also providing corrosion prevention and personnel protection from potential contact burn injuries, slips and falls.


It is for that reason that Belzona has developed an innovative, two-component, polymeric, solvent-free system – Belzona 5871. This multi-functional material provides, in fact, thermal insulation and corrosion protection, whilst improving the safety, efficiency, and durability of industrial equipment.

Single product system, providing insulation, safety, and corrosion protection for hot and cold applications

Belzona 5871 can be applied onto metal pipework, ducting, tank/vessel externals, and other industrial equipment. It is thermally insulating and improves efficiency whilst also preventing contact burn injuries, condensation, and icing. Several tools are suitable to apply the product: a brush, cartridge, or heated airless plural spray. It is therefore ideal for small, complex geometries or rapid application over large areas.

Upon application, the corrosion protecting coating forms a lightweight, high-build closed-cell foam. Due to the foaming epoxy technology, this protective coating expands up to three times its applied thickness e.g. 1mm applied gives 3mm cured thickness, thus increasing the amount of product on the surface. Belzona 5871 is also solvent-free, eliminating the need for any additional primer or top-coats, thus reducing the number of layers needed compared to conventional coating solutions. Moreover, overcoat times are up to 24 hours irrespective of temperature or humidity providing application flexibility. The cure speed and reduced number of layers required, ensure a fast return to service.



Testing the thermal barrier properties of Belzona 5871

In order to test the thermal barrier properties and determine the thickness required to reduce the surface temperature to below 60°C (140°F), we compared a section of uncovered steel substrate and a section of substrate protected with Belzona 5871. For example, Belzona 5871 applied at a thickness of approximately 2.2mm to give a cured thickness of 6.6 mm, will reduce the surface temperature from 120°C (248°F) to below 60°C (140°F). Belzona 5871 is insulating and capable of reducing heat transfer thus providing a safe to touch surface and preventing contact-burn injuries. We confirmed the insulating properties of Belzona 5871 using Lee’s disc method giving a low thermal conductivity of approximately 0.1 W/m.K.


Recommended application thickness of Belzona 5871 to reduce the surface temperature to below 60°C (140°F), to prevent contact burn injuries in accordance with ASTM C1055.

Simulated CUI conditions

Here at Belzona, we simulated CUI conditions using heated pipe sections. The system was repeatedly cycled between 120°C (248°F) and 10°C (50°F) over a period of 1000 hours with alternating wet (with a constant deluge of water at 5 litres per minute) and dry periods. Following the test, the multi-layered systems did not show any blistering, delamination, or cracking and there was no evidence of corrosion.


Salt spray to test the corrosion protection properties

A 35°C (95°F) salt spray was also carried out, in accordance with ASTM B117 on a single layer of Belzona 5871 following two different cure regimes; a 20°C (68°F) cure and 120°C (248° F) post-cure. A vertical 50mm scribe was added to both samples to encourage corrosion. The test samples did not show any signs of failure even after 3000 hours of continuous exposure.


Continuous water immersion to test protection from CUI

We performed a continuous water immersion test, in accordance with ISO 2812-2, where a substrate with a single layer of Belzona 5871, was immersed at 40°C (104°F) in deionised water. The substrate did not exhibit any signs of deterioration after 4500 hours (substrate cured at 20°C/68°F) and 2000 hours (substrate post-cured at 120°C / 248°F).

These tests confirm the excellent corrosion resistance properties of Belzona 5871 under a variety of conditions.


Ice build-up test to challenge the anti-icing and condensation properties of Belzona 5871

We challenged the product’s anti-icing and anti-condensation properties by performing an ice build-up test.
The sub-zero trial was performed on one, two and three layers of Belzona 5871.

Table showing results of ice build-up-test

The test confirmed that Belzona 5871 prevents ice build-up and condensation even at sub-zero temperatures which as a result, prevent CUI.

In conclusion, Belzona 5871 is an innovative solution, providing machinery and equipment thermal insulation to increase efficiency and durability. In addition, the protection against corrosion extends the service life of the equipment, reducing future replacement costs. Belzona 5871 is also a safety-conscious solution, reducing surface temperatures to below 60°C (140°F) to prevent contact-burn injuries.


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