Overview
Polyurea is a two-component polyurethane urea polymer that is sprayed or hand-applied as a liquid and cures within seconds. Because it crosslinks almost instantly, it forms a dense, seamless, chemically-resistant membrane that will not blister, sag or soften the way a conventional epoxy film can.
The Delshine polyurea family covers the full performance range: 100% aromatic spray systems for heavy corrosion service, polyaspartic (3rd generation) systems that cure slowly enough for brush and roller application, single-component hand-applied grades, and pure polyaspartic cast and slip-casting systems. They share a chemistry but they are not interchangeable — each has its own mixing ratio, film build and application window.
Because polyurea cures so quickly, the success of a job is decided long before the gun touches the steel: substrate preparation, primer selection, mixing discipline and equipment calibration determine the result far more than the topcoat chemistry does. This guide walks through each member of the range, the specifications that matter on site, and the practical decisions that separate a five-year membrane from a three-month failure.
Special Thinner for Polyaspartic Polyurea Painting: Reducer / thinner
Product identification
The identifiers below are the ones printed on the drum and quoted on the purchase order. Always order and dispatch by code, because the grade and the zinc or temperature variant cannot be inferred from the trade name alone.
| Product code | — |
|---|---|
| Trade name | Special Thinner for Polyaspartic Polyurea Painting |
| Category | Polyurea coatings |
| System role | Application consumable - thinner / reducer |
| Manufacturer description | Reducer / thinner |
Where this product is used
- Internal lining of crude oil, fuel, chemical and potable water tanks
- Ballast tanks, bilge spaces and other shipboard tank internals
- Chemical bunds, secondary containment and spill containment areas
- Offshore platform decks, risers, splash zones and process equipment
- Water and wastewater treatment tanks, digesters and clarifiers
- Pipeline external coatings, valve bodies and pipe fittings
- Mining, mineral processing and material handling equipment
- Blast walls, shotcrete structures and concrete tunnel linings
How it works in the coating system
A thinner adjusts the viscosity of a coating for the application method and conditions, and it is the correctly matched product that keeps the coating performing as specified after application.
Using the wrong thinner, or too much of the right one, changes the applied film — thinner reduces the solids content of the wet film, which reduces the dry film thickness and can cause adhesion loss, sagging and early failure. This is one of the most common and most avoidable defects in the field.
Purpose in the system: Not part of the coating system itself, but a controlled component of the application process.
Technical properties
The values below are the typical published range for this product family. The exact figures for your batch are confirmed on the batch certificate and the current technical data sheet.
| Role in the coating system | Pure polyurea elastomer — 100 % solids, aliphatic or polyaspartic hybrid |
|---|---|
| Volume solids | 100 % (solvent-free) |
| Mixing ratio by volume | 1:1 by volume (hot spray) · 4:1 by volume (hand applied) · single component (1-pack) |
| Typical dry film thickness | 1.5–3.0 mm typical build; 0.5–1.0 mm for a functional coating |
| Theoretical coverage | 0.4–0.7 m²/litre at 2.0 mm DFT |
| Application methods | Plural-component hot spray (heated to 60–80 °C) · airless spray · brush · roller |
| Application temperature window | 5–35 °C substrate, 15–35 °C ambient; above 40 °C the gel time shortens sharply |
| Suitable substrates | Blasted steel (Sa 2½), concrete, masonry, timber, existing coating |
| Finish / appearance | Coloured, high-gloss or matt; aliphatic grades hold colour and gloss |
| Principal resistance | Abrasion, impact, hydraulic fluid, fuel, caustic and salt spray |
| UV resistance | Aliphatic and polyaspartic grades: excellent. Aromatic grades: poor — needs an aliphatic topcoat |
| Adhesion to prepared steel | > 6 MPa tensile pull-off on prepared steel |
| Salt spray performance | > 4,000 h in a 5 % salt spray chamber on a 3 mm film |
| Chemical resistance | Excellent against dilute acids, alkalis, oils and fuels |
| Abrasion resistance | Excellent — the standard choice for bunds, ramps and wear areas |
| Flash point | 85–95 °C (aromatic grades) |
| Shelf life | 12 months unopened, stored between 5 and 35 °C |
| Density | 1.05–1.20 g/cm³ |
| Pack sizes | 1 kg · 4 kg · 8 kg · 10 kg · 20 kg · 25 kg · 200 kg · 230 kg drums |
Surface preparation
- Abrasive blast the substrate to at least Sa 2½ (ISO 8501-1) using angular garnet or aluminium oxide media. Polyurea will not adhere to a merely cleaned surface — the mechanical key created by blasting is what carries the load.
- Remove every trace of dust, oil, grease, salt and soluble corrosion product with a clean, oil-free blast. Vacuum the surface and re-blast any contaminated zone rather than trying to paint over it.
- Check the steel for pitting. Deep pitting must be welded out and ground flush before coating — polyurea bridges a pit but does not fill it.
- Round all edges to a minimum 2 mm radius and grind welds smooth. Polyurea applied over a sharp edge will pull back and expose a thin wedge of bare metal.
- Control the environment. Spray polyurea needs a dry substrate, no dew point within 3 °C, ambient above 10 °C and relative humidity below 75%.
- Apply the specified primer while the substrate is still metallically clean and slightly tacky. Do not let the primer fully cure before topcoating — intercoat adhesion is better on a B-cured primer.
- Mask or plug threaded connections, drain openings and vent nozzles before spraying. Polyurea is very difficult to remove once it has cured.
Application procedure
Add the thinner slowly to the paint with good agitation, never the other way round.
Measure the replacement by volume against the coating weight and the recommended percentage on the data sheet. A mixing gauge should be used for two-pack systems.
Add only what is needed for the current temperature and spray setup, because the viscosity will change as the can sits.
Mixing, ratio and induction time
Not applicable — the thinner itself is a single component. It must never be mixed with a different thinner family, and surplus thinned paint must never be returned to the original container.
Cure, recoat window and service readiness
Not applicable. The thinner evaporates during application, and the coating's own cure schedule applies from that point.
Coverage and thickness calculation
Not applicable. As a rule of thumb, replacing more than 10% of the paint volume with thinner reduces the achieved DFT below specification — which is why the replacement percentage must be limited and recorded.
Technical note. Coverage (m²/litre) = (volume solids × 10) / DFT (µm)
Worked example
| Specified DFT | 2000 µm |
|---|---|
| Volume solids | 100 % |
| Theoretical coverage | 0.50 m²/litre |
| Total for the area | 100 m² → 50.0 litres |
Advantages
- Cures in seconds to minutes, so a tank can be returned to service the same day instead of waiting a week for an epoxy to harden.
- 100% solids chemistry — no solvent to evaporate, so there is no solvent-trapped film and no VOC contribution to the plant.
- Outstanding abrasion, impact and chemical resistance, including resistance to hydrocarbons, acids, alkalis and salt water.
- Seamless, pinhole-free membranes that can be built to any thickness in a single pass without the layer-count of a conventional system.
- Excellent UV and weather resistance in aliphatic and polyaspartic grades, with no chalking or yellowing over a service life measured in decades.
- Low temperature sensitivity compared with epoxies — some polyaspartic grades can be applied down to -10 °C.
Limitations and precautions
- Aromatic 1st generation polyurea discolours badly under UV — it must be topcoated with an aliphatic or polyaspartic finish for exterior work.
- Surface preparation is unforgiving. Polyurea applied over contaminated or under-blasted steel will fail at the interface, not in the film.
- Spray polyurea demands correctly calibrated plural-component equipment. A worn nozzle or a mis-set proportioning pump will produce an off-ratio film with poor properties.
- The fast gel time leaves almost no working time — a pause in spraying can leave a cold joint or a wet edge.
- The material is expensive and the equipment is capital-heavy, so polyurea only makes economic sense on jobs where the fast cure or the chemical resistance genuinely pays for itself.
Storage and shelf life
- Store component A and component B separately in their original containers, in a cool, dry, ventilated store between 5 °C and 35 °C.
- Never store A and B at a temperature above 40 °C and never allow the drums to freeze — a frozen component will not mix correctly and must be thawed and re-homogenised before use.
- Keep the drums sealed. Component A of an aromatic system can react with atmospheric moisture and will form a skin in an open drum.
- Rotate stock using first-in-first-out. Typical shelf life is 12 months for unopened drums and considerably shorter once opened.
Safety, PPE and ventilation
- Both components contain isocyanates. Always work with local exhaust ventilation and wear a supplied-air respirator or a properly fitted organic-vapour cartridge mask.
- Wear chemical-resistant gloves, safety goggles and a coverall. Isocyanate vapour sensitises the respiratory system permanently.
- Do not spray near open flames, hot work or hot surfaces. Isocyanate vapour can ignite at elevated temperatures.
- Ensure the spray booth is negatively pressurised so overspray and vapour are drawn away from the operator.
- Dispose of empty drums through a licensed chemical contractor. Do not burn or bury residue.
Quality control and inspection
- Confirm the thinner family matches the coating being applied.
- Record the volume of thinner added to each batch.
- Check the mixed viscosity with a flow cup or by the manufacturer's specified method.
Pricing and how to order
Delshine quotes this product per square metre at a specified dry film thickness, or per drum/litre depending on the project. The material cost is usually the smallest part of the installed cost — surface preparation, access and application labour dominate. Send us the substrate, the service conditions and the required DFT and our technical team will return a full system recommendation with a firm price.
Polyurea is priced per square metre of applied film, not per kilo of material, because coverage depends entirely on the target dry film thickness. At 2 mm, a kilo of two-component polyurea covers roughly 0.5 m², so a 1,000 m² tank needs close to two tonnes of material including waste. Always quote on DFT plus primer, not on area alone.
Frequently asked questions
The questions below are the ones our technical team is asked most often about this product family.
How fast does polyurea actually cure?
Aromatic spray polyurea reaches handling strength in seconds and is walkable in 10-20 minutes. Polyaspartic grades cure far more slowly — typically 2 to 8 hours to a tough film and up to 7 days for full chemical resistance. Single-component grades fall between the two. Always confirm the gel and recoat times on the specific product data sheet before scheduling work.
Can polyurea be applied over concrete?
Yes, and it is one of its strongest applications. The concrete must be sound, dry and free of laitance, and it should be abraded or shot-blasted to open the surface. Prime with a concrete-compatible epoxy or polyurethane primer, then apply polyurea. On damp concrete a moisture-tolerant epoxy primer such as GH900 is required.
Can polyurea be sprayed in cold weather?
Hot-spray aromatic polyurea can typically be sprayed down to about 5 °C substrate temperature with a heated set-up. Polyaspartic grades are far more forgiving and some can be applied down to -10 °C. Below that, use a heated substrate or consider an epoxy or polyurethane system instead.
Does polyurea need a topcoat?
For internal, submerged or enclosed service, no — a full-build polyurea membrane is self-sufficient. For exterior service, yes: aromatic spray polyurea discolours under UV, so it is normally finished with a light-stable aliphatic polyurethane or polyaspartic topcoat. This also improves gloss retention and makes future inspection easier.
What mixing ratio does polyurea use?
It depends entirely on the grade. Hot-spray aromatic systems are normally 1:1 by volume. Hand-applied polyaspartic systems are typically 4:1 by volume. Pure polyaspartic grades vary again. Never mix by eye or by weight unless the data sheet explicitly says to — use a proper proportioning pump or a measured pot system.
How much polyurea do I need per square metre?
At a 2 mm dry film thickness, one litre of sprayed polyurea covers roughly 0.5 m². At 1.5 mm it covers about 0.67 m², and at 3 mm roughly 0.33 m². Multiply the surface area by the coverage figure, then add 10-15% for waste, overspray and rework.
What primer should I use under polyurea?
A two-component epoxy primer with good surface tolerance is the standard choice on steel — for example a zinc-rich epoxy or a high-build modified epoxy anticorrosive primer. Polyurea will not reliably adhere directly to bare or poorly prepared steel, and it is not compatible with alkyd or phenolic primers.
How long will polyurea last?
A correctly specified 2-3 mm aromatic polyurea membrane in continuous immersion or buried service typically gives 15-25 years. Polyaspartic topcoated systems give 10-20 years exterior. Aggressive chemical service, poor surface preparation and operating temperatures above the product limit will cut that dramatically.
Related products
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