Arcstruct PU 420 Polysiloxane Topcoat
Two-pack epoxy-siloxane hybrid finish for C5 atmospheric exposure and long maintenance intervals, applied in a single heavy coat. Gloss and colour retention are higher than a conventional polyurethane, and the higher build allows a two-coat system to replace three in some specifications.
Grade Arcstruct PU 420 | Range Industrial and Infrastructure Coatings | Technology Two-pack epoxy-siloxane hybrid, solvent-borne
Technical Data Sheet
Arcstruct PU 420
Issue 2026.09
1. Product description
Epoxy-siloxane hybrid finish for C5 atmospheric exposure and long maintenance intervals, where the cost of returning to the asset dominates the cost of the coating. Gloss and colour retention are higher than a conventional polyurethane and the film is applied at a higher build, so a two-coat system can replace three in some specifications. Specified where inspection access is difficult or the repaint cycle is long.
2. Features
- Gloss and colour retention above a conventional polyurethane
- Single heavy coat at a build above the polyurethane band
- Allows a two-coat system in some specifications
- Moisture-assisted siloxane cure
- For assets with difficult inspection access or long repaint cycles
3. Recommended uses
Topcoat for C5 atmospheric systems on structures and plant where returning to the asset costs more than the coating, including two-coat systems over Arcstruct PR 450 zinc-rich primer.
Substrates. Arcstruct EP intermediate coats, Arcstruct PR 450 zinc-rich primer in a two-coat system, aged polyurethane after abrasion
4. Typical properties
| Property | Typical value | Method |
|---|---|---|
| Technology | Two-pack epoxy-siloxane hybrid, solvent-borne | Formulation |
| Gloss | Above 70 at 60 degrees, with retention reported against the weathering cycle | ISO 2813 |
| Colour | To the agreed colour reference | Visual |
| Volume solids | 70 to 80 per cent | ISO 3233-1 |
| Density, mixed | 1.3 to 1.6 g/cm3 | ISO 2811-1 |
| Dry film thickness per coat | Above the 50 to 80 micrometre polyurethane topcoat band, applied as a single heavy coat to the dry film thickness named in the system specification | ISO 2808 |
| Accelerated weathering | 1000 to 2000 hours fluorescent UV with condensation cycling, with gloss retention and colour change reported | ISO 16474-3 or ASTM G154 |
| Solvent resistance, fully cured film | 50 to 100 MEK double rubs without softening | ASTM D5402 |
| Neutral salt spray resistance, complete system | 1000 hours or more, the test duration rising with the ISO 12944-6 regime for the C5 durability range specified, rated for blistering, rusting and undercutting | ISO 9227, duration to ISO 12944-6, rated to ISO 4628-2, -3 and -8 |
| Chemical resistance, spot and immersion | Assessed against the named chemical and cleaning agent list for the site, with softening, blistering and colour change reported | ISO 2812-1 and ISO 2812-3 |
Typical values, not a specification. Values for each batch are given on its Certificate of Analysis.
5. Application
| Parameter | Guidance |
|---|---|
| Application method | Airless or conventional spray in a single heavy coat. |
| Substrate | Arcstruct EP intermediate coat within its overcoating interval; Arcstruct PR 450 in a two-coat system, following the mist coat practice over the inorganic grade; aged polyurethane abraded and cleaned. |
| Mixing | Base and hardener mixed at the stated ratio. Pot life is short, so only the quantity that can be applied within it is mixed. |
| Film thickness | Single heavy coat above the 50 to 80 micrometre polyurethane topcoat band, to the dry film thickness named in the system specification; wet film checked with a comb and dry film verified to ISO 2808. |
| Conditions | Not applied below the stated minimum substrate temperature. Substrate at least 3 degrees Celsius above the dew point during application and initial cure. |
| Cure | Cure proceeds by hydrolysis and condensation of the siloxane and is moisture assisted, so low humidity or a dry winter shop extends the through-cure time. |
Process. Airless or conventional spray in a single heavy coat. Two-pack, short pot life, cure proceeds by hydrolysis and condensation of the siloxane and is therefore moisture assisted, so low humidity extends the through-cure time. Not applied below the stated minimum substrate temperature
6. Storage and handling
Store in the original closed containers under cover, dry and out of direct sun, at 5 to 35 degrees Celsius, and reseal the hardener immediately after use because it reacts with atmospheric moisture. Shelf life is stated on the label and the Certificate of Analysis. Handle and use the product in line with its Safety Data Sheet.
7. Safety and regulatory information
Read the Safety Data Sheet before use. Safety Data Sheets and regulatory declarations are issued by our technical centre against the product and batch supplied, so they are sent on request rather than published. Request a Safety Data Sheet or declaration.
This Technical Data Sheet is published for on-screen reference. The information is given in good faith from laboratory and application experience and describes typical values; it is not a specification and does not replace a trial on your own substrate and line. Arctic Materials may revise this sheet without notice. Issue 2026.09.
Technical Data Sheets on this site are for on-screen viewing. For a controlled copy, write to tech@arcticmaterials.com.
Other grades in this range
Need a Safety Data Sheet, a regulatory declaration or a grade specified to your line? Contact our technical centre.