Arcstruct PR 450 Zinc-Rich Primer, organic and inorganic grades
Zinc-rich primer for blast-cleaned carbon steel, supplied as an organic two-pack epoxy grade and an inorganic ethyl silicate grade, both formulated to the metallic zinc content recognised for zinc-rich primers in ISO 12944-5. Metallic zinc in electrical contact with the steel gives cathodic protection at scratches and cut edges in long durability systems.
Grade Arcstruct PR 450 | Range Industrial and Infrastructure Coatings | Technology Zinc-rich primer: two-pack epoxy (organic grade) or moisture-curing ethyl silicate (inorganic grade), solvent-borne
Technical Data Sheet
Arcstruct PR 450
Issue 2026.09
1. Product description
Zinc-rich primer supplied in an organic epoxy grade and an inorganic ethyl silicate grade, both formulated to the metallic zinc content bands recognised in ISO 12944-5 for long durability systems. The organic grade is the site and fabrication choice, tolerant of overcoating and of touched-up areas, while the inorganic grade gives a harder, more heat-tolerant film for high durability and for service above the limit of an organic binder. Both provide cathodic protection at scratches and cut edges rather than relying on barrier alone.
2. Features
- Cathodic protection at scratches and cut edges, not barrier alone
- Organic epoxy grade for fabrication and site work, tolerant of overcoating and touch-up
- Inorganic ethyl silicate grade for a harder, more heat-tolerant film
- Organic grade accepts the intermediate coat directly
- Inorganic grade cure confirmed by solvent rub before overcoating
3. Recommended uses
Primer for structural steel, plant and equipment in long durability atmospheric systems, with the inorganic grade used for high durability and for steel in service above the temperature limit of an organic binder.
Substrates. Blast-cleaned carbon steel to ISO 8501-1 Sa 2.5, Sa 3 preferred for the inorganic grade
4. Typical properties
| Property | Typical value | Method |
|---|---|---|
| Technology | Zinc-rich primer: two-pack epoxy (organic grade) or moisture-curing ethyl silicate (inorganic grade), solvent-borne | Formulation |
| Appearance | Grey, matt metallic zinc film | Visual |
| Zinc dust content, non-volatile matter | At or above the minimum that ISO 12944-5 sets for a zinc-rich primer; the confirmed value is issued with the Certificate of Analysis | ISO 12944-5 definition; metallic zinc in the cured film to ASTM D6580 where the specification calls for it |
| Volume solids | 55 to 70 per cent, set by grade | ISO 3233-1 |
| Density, mixed | 2.4 to 3.0 g/cm3, set by zinc loading | ISO 2811-1 |
| Dry film thickness per coat | 40 to 80 micrometres | ISO 2808 |
| Solvent resistance, fully cured film, organic grade | 50 to 100 MEK double rubs without softening | ASTM D5402 |
| Cure before overcoating, inorganic grade | Resistance rating 4 to 5 after 50 MEK double rubs | ASTM D4752 |
| Adhesion, pull-off from blast-cleaned steel, organic grade | Typically 5 to 15 MPa, cohesive failure preferred over adhesive | ISO 4624 or ASTM D4541 |
| Neutral salt spray resistance, complete system | 720 to 1000 hours or more, set by the ISO 12944 corrosivity category and durability range, rated for blistering, rusting and undercutting | ISO 9227, rated to ISO 4628-2, -3 and -8 |
Typical values, not a specification. Values for each batch are given on its Certificate of Analysis.
5. Application
| Parameter | Guidance |
|---|---|
| Application method | Airless spray with continuous agitation of the pot to keep the zinc in suspension. Small repairs, including repairs to the inorganic grade, are made by brush with the organic grade. |
| Surface preparation | Blast-cleaned to Sa 2.5 to ISO 8501-1 for the organic grade, Sa 3 preferred for the inorganic grade, with a medium grade profile to ISO 8503-2. Soluble salts on previously exposed steel sampled to ISO 8502-6, measured to ISO 8502-9 and held typically below 20 to 50 mg per square metre as chloride. Prime before any visible re-rusting. |
| Mixing | Zinc component fully dispersed into the binder and the mix strained before use. The organic grade is mixed at the stated ratio with the stated induction time and used within the pot life. |
| Film thickness | 40 to 80 micrometres dry per coat, verified to ISO 2808. The inorganic grade is not over-applied, since excess build can mud crack. |
| Conditions and cure | Substrate at least 3 degrees Celsius above the dew point during application and initial cure. The organic grade cures at ambient temperature as a two-pack epoxy. The inorganic grade cures by reaction with atmospheric moisture and needs relative humidity above about 50 per cent; a dry shop slows its cure. |
| Next coat | The organic grade accepts Arcstruct EP 240 directly. Over the inorganic grade, cure is confirmed by solvent rub, then a thin mist coat is applied and allowed to flash off before the full intermediate coat, so that solvent escaping from the porous film does not gas and pinhole the wet layer. |
Process. Airless spray with continuous agitation of the pot to keep the zinc in suspension. The organic grade is a two-pack ambient cure epoxy and accepts the intermediate coat directly. The inorganic grade is an ethyl silicate that cures by reaction with atmospheric moisture and needs relative humidity above roughly 50 per cent, is checked for cure by solvent rub to ASTM D5402, and takes a thin mist coat before the full intermediate coat because solvent escaping through the porous film will otherwise gas and pinhole the wet layer
6. Storage and handling
Store in the original closed containers under cover, dry and out of direct sun, at 5 to 35 degrees Celsius, keeping the inorganic binder tightly closed because atmospheric moisture starts its cure. 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
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