PRIMER / UNDERCOAT · THE FOUNDATION
2K EPOXY PRIMER
GP3401
Germa-Tech Epoxy Primer gives excellent rust proofing for bare metal, good adhesion power to steel, aluminum and galvanized steel.
SCAN FOR THE FULL RANGE,
APPLICATION GUIDES & VIDEOS
germatech.com.au
TDS v2.3 · ISSUE 02.09.2026
SUPERSEDES 07.2022
REVIEW DUE 07.2028
3.5 : 1 : 1 (30%-35%)
BY VOLUME
4-6 hours
20 °C · with Hardener
GRAVITY 1.4-1.8 mm · SUCTION 1.7-2.0 mm
HVLP 2.0 bar · RP 2.0-2.5 bar · CONV 3-4 bar
2.5 coats (1 light tack coat + 2 solid coats)
At 20 °C 5-10 minutes between coats*
*ADJUST FOR THE DAY'S TEMPERATURE
Allow 15-20 minutes air drying time before force drying*
SKIP THIS AND YOU GET SOLVENT POP
40-60 minutes
60 °C METAL TEMPERATURE
01SUITABLE SUBSTRATES
- Sanded and dried existing finishes.
- Sanded steel, iron, galvanised steel, aluminum, and fiberglass.
- Plastic automotive parts require plastic primer application.
02SURFACE PREPARATION
Remove Wax, Silicon and other contaminants with Germa-Tech Prepsol
03MIXING
| TEMPERATURE | PRIMER | HARDENER | REDUCER |
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| >30 °C | GP3401 | GP3402 | GP3403 |
| Ratio by volume | 3.5 : 1 : 1 (30%-35%) |
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| Spray viscosity | 16-18 s (DIN4, 20 °C) |
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| Pot life | 4-6 hours at 20 °C (with Hardener) |
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| Tinting | NOT TINTABLE. Epoxy chemistry does not accept 2K colour — do not tint this primer. For a tinted ground coat use a Germa-Tech 2K primer surfacer (8% 2K colour). |
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| Notes | The TDS mixing table shows only a '>30 °C' row; no other temperature bands are given. |
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BEFORE YOU START — THE SYSTEM IS THE PROCESSGerma-Tech abrasives and ancillary products are graded and tested for compatibility with this product and the process on this sheet — that control is what makes any problem on the job assessable and fixable. Once a non-Germa-Tech product has been used at any step, what actually touched the panel can no longer be verified, and issues that arise cannot be fairly assessed — by us or by anyone. Use the system through the whole process, and if something on this sheet does not fit the job,
talk to us before you spray. Refer to the
GERMA-TECH APPLICATION STANDARD.
04APPLICATION
| Gun — gravity feed | 1.4-1.8 mm |
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| Gun — suction feed | 1.7-2.0 mm |
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| Pressure — HVLP | 2.0 bar |
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| Pressure — RP | 2.0-2.5 bar |
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| Pressure — conventional | 3-4 bar |
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| Coats | 2.5 coats (1 light tack coat + 2 solid coats) |
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| Flash-off between coats | At 20 °C 5-10 minutes between coats |
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| Flash-off before bake | Allow 15-20 minutes air drying time before force drying |
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| Dry film build | 40-60 µm total |
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05DRYING & CURING
| TEMPERATURE | DRY |
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| 20 °C | 18-26 hours |
| 60 °C | 40-60 minutes |
BAKE TEMPERATURE IS METAL TEMPERATUREBake time starts when the panel reaches temperature, not when the door shuts. A cold panel in a 60 °C booth takes roughly ten minutes to get there — add that to the schedule or the film is under-cured.
06COATING THICKNESS — WHERE THIS SITS IN THE STACK
Sealer / wet-on-wet
25-35 µm
2K primer surfacer
50-80 µm
Body filler
shaped back — not film
THIS PRODUCT · GP3401 ▶
40-60 µm total
SUBSTRATE
bare steel / prepared panel
FULL BUILD
170-270 µm of 300
Read it like the panel: substrate at the bottom, clear on top. Faded rows are the rest of the system at its normal build. See the Coating Thickness Guide.
07RECOAT & REWORK
| Recoat — this product over itself | TOPCOAT WINDOW — 24 hours at 20 °C panel temperature from application, IF NOT BAKED: a Germa-Tech finish coat may be applied direct within it. After any bake cycle the window is ZERO — the bake closes the film, abrade and degrease before recoating. ONCE SANDED the clock restarts: 24 hours from sanding to recoat or apply the next coat (colour). Past 24 hours from sanding, sand again before coating. Heat shortens the unbaked window; the 24-hour sanded window does not move — a sanded surface is limited by contamination, not cure. |
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| The next coat over this | Epoxy → next coat: within the 2-hour unbaked window, or within 24 HOURS of SANDING; past that, sand again. GP-EP1 may be top-coated with direct gloss WET ON WET after 30 minutes minimum at 25 °C — no basecoat systems or single-pack topcoats unless fully cured. |
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HOW EACH COAT BONDS — WHY EVERY WINDOW ON THIS SHEET CLOSESThe whole repair is designed as
one system applied within one overall time frame: the primer is dried and sanded, but from colour onward it is a concurrent, same-day process — and every window on this sheet exists to keep you inside it. Within its window the next coat fuses chemically with the film beneath; past it, the film has cured and adhesion must be made mechanically — abrade, degrease, recoat. Heat closes windows sooner: cure runs on temperature, not the clock. Straying from the timed system — jobs interrupted, held over, stretched — is where the problems start. Full explanation in the
GERMA-TECH APPLICATION STANDARD.
If in doubt, abrade. IF YOU MISS THE RECOAT WINDOWOnce the film has cured past its recoat window, do not put another coat straight over it — the new coat sits on the surface and lets go at the interface. Abrade the whole area first (P800 wet or a grey abrasive pad), degrease, tack off, then recoat.
08SANDING GUIDE — STEPS, GRITS & ABRASIVES
| Step | Grit | What you are doing | Germa-Tech abrasives — examples by part number |
|---|
| 1 · Within the window | no sanding | Inside the recoat window (see RECOAT & REWORK) the next coat bonds chemically — apply straight over, no abrasion needed. | — |
| 2 · Cured — flat areas | P240–P320 dry | Once the epoxy has cured past its window, sand before hi-fill or colour. P240 to cut and level, P320 to finish. | ORBIT GOLD 150 mm P240 (M6-P240-100) · P320 (M6-P320-100) · CERAMIC MESH 150 mm P240 (MS6-P240-10) — mesh clears the dust an epoxy loads up |
| 3 · Contours & edges | fine pad | Swages, folds and edges a disc cannot reach — scuff to a uniform matt. | SCOTCH BRIGHT RED pad 400G (A705-1) · SHEER ROLL FOAM 115 P320 (GFR320) |
EPOXY SANDING — WHAT MATTERSEvery square millimetre going under the next coat must be uniformly matt — any glossy spot is a spot with no key. Epoxy sands with a soapy, loading cut: keep the paper moving, clear the dust often, and let mesh or fresh discs do the work. After sanding, the 24-hour from-sanding window on this sheet starts — a GT HOUSE RULE, deliberately stricter than published practice (no other manufacturer publishes a maximum from sanding) — recoat within it or re-scuff.
LARGE JOBS — WHEN SANDING TAKES MORE THAN A DAY: on bigger jobs the panels sanded first can be outside the 24-hour window before the last panel is finished. Give the whole job a light scotch rub immediately before colour goes on, and a coat of wet-on-wet primer (GP3201 System 1) is also advised — it seals off any imperfections and puts a fresh, uniform surface under the colour.
THE 100-GRIT RULE — WHY THE SEQUENCE MATTERSEach grit exists to remove the scratches left by the one before it. Never jump more than about 100 grit in one step — a P80 scratch will not come out with P400; it gets buried, then telegraphs through the topcoat weeks later as sanding-mark showthrough. Work the sequence, prove the panel with a guide coat, and step down evenly.
THESE STEPS ARE A WARRANTY CONDITIONFollowing the steps and grits above — with
Germa-Tech abrasives — is a condition of product warranty, not a suggestion. P-grades are only comparable within a controlled range: a recent claim traced to an ungraded brand’s “P320” that cut like a true P240, leaving scratch in the primer that showed through the finished clear. The part numbers above are graded and tested for compatibility with this product and this process — which is what makes a fault assessable: once non-Germa-Tech product has been used, what touched the panel can no longer be verified, and issues arising cannot be fairly assessed. Refer to the
GERMA-TECH APPLICATION STANDARD.
09PHYSICAL PROPERTIES
| Coverage | about 3.6-4.3 m²/L in practice (6.6 m²/L theoretical at 50 µm) Estimate, not a measurement. Indicative coverage at 50 µm dry film thickness, assuming 100% transfer efficiency. Real-world coverage is lower — spray guns lose material as overspray. Allow 55-65% of the theoretical figure. |
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| Density | approx. 1.40 (relative density, water = 1) — estimated from the Safety Data Sheet; not separately measured |
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| Gloss | N/A — not applicable to a primer |
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| Equipment cleaning | Clean guns and equipment immediately after use with gun wash or a solvent cleaner. Never let mixed 2K product start to cure in the gun — once it kicks, no solvent will save it. |
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10STORAGE, SHELF LIFE & PACKS
| Storage life (unopened) | Up to 36 months unopened — SUBJECT TO correct storage: a cool, dry place below 20 °C, out of direct sun. Heat is the biggest killer of paint in the tin: stock stored or transported in hot vehicles, tin sheds, shipping containers or direct sunlight loses life fast whatever the date on the tin, and that is where most premature failures start. Storage life is an optimal guide, not a promise that survives a hot shed. |
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| Once the seal is broken | Once the seal is broken the clock starts, and how you store it sets the pace. This product: 14 DAYS once the seal is broken, then discard.
All hardeners: 14 days once opened — then discard. Hardener is sealed without air; the moment air enters it starts to deteriorate. A part-used tin resealed tight lasts the 14 days; a loose lid does not. |
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| Storage | Store indoors in a cool, dry place below 20 °C, out of direct sunlight, with the lid sealed tight after every use. Never store or transport in heat — not in a tin shed, a shipping container, a hot van or a sunlit rack. |
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| Pack sizes | 5kgs |
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11PRODUCT CODES
| CODE | WHAT IT IS | PACK SIZE |
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| GP3401 | Product | 5KG |
| GP3402 | Hardener | 1LT |
| GP3403 | Reducer | 1LT |
COMPLETE KITEPOXY PRIMER GP3401 + HARDENER GP3402 + REDUCER GP3403
12WHERE IT SITS IN THE SYSTEM
BARESUBSTRATE
›
EPOXYPRIMER
›
FILLER
›
2K PRIMERSURFACER
›
SEALERWET-ON-WET
›
COLOUR
›
CLEAR
The highlighted step is where this product sits in the repair. Ancillaries support every step.
13STANDARD NOTES — THE SAME ON EVERY SHEET IN THIS SET
- Below 15 °C, air drying at ambient temperature is not recommended — allow a full bake at 60 °C metal temperature. SN1 · ALL BAKEABLE SPRAYED PRODUCTS
- Mix to the stated ratio and use the mix within its pot life. Only use Germa-Tech hardener and reducer — never interchange with another brand. SN2 · ALL MIXED 2K
- At low humidity, a flash-off of 2-3 minutes between coats helps achieve a smooth film. SN3 · ALL SOLVENT-SPRAYED
- Above 30 °C ambient, add Retarder Solvent or move to the slow reducer to avoid blushing — refer to the Retarder Solvent TDS. SN4 · ALL SOLVENT-SPRAYED
- Fisheyes during application: add 0.5-1% Anti Silicon to the remaining paint and respray the affected area. SN6 · ALL SOLVENT-SPRAYED
- Total coating thickness on the panel — every layer together — must not exceed 300 µm. Refer to the Germa-Tech Coating Thickness Guide. SN7 · ALL FILM-BUILDING
- Do not dry in direct sunlight — panel temperatures in direct sun can exceed 70 °C. Allow 24 hours or a full bake. SN9 · ALL BAKEABLE SPRAYED PRODUCTS
- Germa-Tech products are designed to work as a system — fillers, primers, basecoat, clears, hardeners, reducers, abrasives and ancillaries — each graded and tested for compatibility with the products and processes on this sheet. Performance is only assured within the system, and a fault is only assessable within it: once non-Germa-Tech product has been used in the process, what touched the panel can no longer be verified. SN10 · ALL PRODUCTS
- *Flash-off times are measured at the stated temperature and MUST be adjusted for the day: colder than stated = LONGER flash, warmer = shorter. In winter, shops painting below 23 °C routinely under-flash — solvent is still in the film when the next coat lands. Below 15 °C, extended flash and air dry are not enough: bake the job. SN13 · ALL PRODUCTS WITH A FLASH-OFF
- 2.5 COATS means: start with a LIGHT TACK COAT, let it flash, then apply 2 solid coats — and STOP. Less is best. The tack coat sets adhesion and control; the two solid coats do the work. Extra coats add solvent load and film build, not quality. The tack coat and the 24-hour from-sanding rule are GT HOUSE RULES — taught and enforced here, deliberately tighter than published industry practice. The teaching behind this — Application Standard, section 03. SN14 · ALL 2.5-COAT PRODUCTS
- FINISH FOR COLOUR — THE STANDARD GRADE. The last sanding pass before colour is P500-P600 dry (or P800 wet). METALLIC AND PEARL COLOURS REQUIRE P800, dry or wet — coarser scratches telegraph through the flake and show in the finish. Any coarser grits on this sheet are shaping or stripping stages, not the finish. SN16 · FINISH FOR COLOUR
Standard inclusions are controlled: each note applies to every product in its named set, enforced at build. They cannot drift onto some sheets and off others.
14PRODUCT-SPECIFIC NOTES
- 1. For oxidized iron and cast iron, shot blasted sa2.5 class with roughness of 30-75um, or acid wash the oxidized parts
- 2. It is recommended to bake at 60-70 for 30 minutes when temperature is below 10 °C for better curing of the paint film.
- 3. Choose the right hardener and thinner to avoid poor curing paint film.
- 4. Product must be cured before application of 2k Primer or Wet on Wet Primer
- 5. Cured product must be sanded immediately before application of primer
- 6. Top coat colour can be applied directly to cured and sanded Epoxy Primer, this process is recommended only for industrial applications and not automotive applications. For automotive applications a 2k primer or wet on wet should be applied prior to top coat.
AMBIENT TEMPERATURE — WHY EVERY TIME ON THIS SHEET MOVESEvery time on this sheet — flash-off, drying, pot life, the recoat window — is quoted at 20-23 °C, and every one of them moves with temperature, because the two things that set them, solvent evaporation and chemical cure, are both driven by heat. As a working rule cure rate roughly doubles for every 10 °C rise: at 30 °C the times run at about half; at 15 °C they stretch to nearly half speed. Judge by panel temperature, not air temperature — a panel in sun or fresh out of the booth is far hotter than the shed.
HOT WEATHER (above 30 °C): everything shortens. Flash-off comes down, pot life comes down, and the recoat window closes early. Move to the SLOW hardener and slow or extra-slow reducer so the film has time to flow and release solvent — spraying standard speeds in heat is the fast road to dry spray and solvent boil.
COLD WEATHER (below 20 °C): everything stretches. Flash-off gets LONGER — the most common winter mistake is coating over a film that looks flashed but has not released its solvent, which traps it under the next coat and comes back as fry-up, dieback or runs. Move to the FAST hardener, and extend every flash. Below 15 °C standard 2K cure effectively stalls — bake the job, or wait for heat. Cold does not extend the recoat window in proportion either: contamination, moisture and flash rust run on the clock regardless of temperature.
15GOOD TO KNOW — WHAT WE GET CALLED ABOUT
- Below 10 °C, bake 30 minutes at 60-70 °C or the film will not cure properly.
- It must be cured before 2K primer or wet-on-wet primer goes over it.
- Sand the cured epoxy immediately before the next primer goes on - don't leave it sitting.
- Topcoat direct over epoxy is an industrial call only. Automotive work gets a 2K or wet-on-wet first.
- Oxidised iron and cast iron need shot blasting to Sa2.5, 30-75 µm profile, or an acid wash.
16TROUBLESHOOTING
| DEFECT | WHAT YOU SEE | WHY IT HAPPENED | FIX |
|---|
Rust breakthrough | rust staining or blistering pushing up through the finish, usually along a repair edge, a weld, a stone chip or a panel bottom | bare or rusted metal coated without proper treatment, filler or surfacer put straight on bare steel and left, oxidation forming between prep and priming, or a coating not cured hard enough to seal | cut the corrosion out back to sound clean metal, epoxy prime, then rebuild the system |
Delamination and peeling | a coat lets go of the one under it - the film peels, flakes or lifts off cleanly in sheets, often starting at an edge or a stone chip | the surface underneath was not keyed or was not clean - missed degrease, wrong or no undercoat, sanding grit too fine or missed altogether, recoat window blown, or basecoat left too long before clear | remove all the loose film back to a sound layer, feather the edge, re-prime and rebuild the system properly |
Soft film and slow cure | the film stays soft, marks under a fingernail or a mask edge, clogs the paper when sanded and will not polish up | wrong or short-measured hardener, mixing beyond pot life, spraying too cold, bake cut short or started before the flash was finished, or a drying additive used where a hardener is needed | give it a full bake cycle and re-check; if it is still soft the film has to come off back to a sound layer and be redone with the correct mix |
Blistering | small raised bubbles or pimples in the film, from about 0.5 mm up, sometimes appearing days or weeks after the job | moisture or contamination trapped under the film - water or oil in the air line, a panel not dried after washing, wet-sanded filler primed before it dried, high humidity during application, or the substrate not degreased | sand the blistered layers off down to a sound layer or the substrate, re-prime and refinish |
Lifting and wrinkling | the film shrivels, swells or folds into wrinkles while the new coat is going on or shortly after | solvent in the new coat attacking a sub-layer that is not solvent-proof - 1K primer or thermoplastic paint under a 2K coat, a coat put over an under-cured film, an over-long flash, or a coat put on outside its recoat window | let the affected area dry hard, sand the lifted film off down to a sound layer, prime past where the lifting stopped, and refinish |
Sanding-mark showthrough | the sanding scratch pattern from the stage underneath telegraphs through the finished film, often as fine parallel lines or DA swirls | grit too coarse for the coat going over it, the undercoat not fully cured before it was sanded, or the finish grit skipped so a coarse scratch was never removed | sand the area back flat at the correct finishing grit, re-prime, and refinish |
AUSTRALIAN CONDITIONSAbove 30 °C ambient, move to the slow hardener and slow reducer and expect flash-off to shorten — dry spray and blushing are what a standard system gives you through a hot afternoon. Below 15 °C, air drying is not recommended: bake. In coastal and high-UV areas do not shortcut the epoxy step on bare metal.
17HEALTH & SAFETY
EPOXY / AMINE HARDENER — SENSITISERThis is an epoxy system. The hardener is amine cured — it contains
no isocyanate, so the isocyanate health-monitoring requirement does not apply, but epoxy resins and amine hardeners are skin and respiratory sensitisers and sensitisation is usually permanent. Avoid all skin contact, wear nitrile gloves and change them often, and use respiratory protection selected under AS/NZS 1715. Refer to the Safe Work Australia
Model Code of Practice: Spray painting and powder coating.
Read the Safety Data Sheet before use. REVISION HISTORY
| VERSION | DATE | CHANGE |
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| v2.3 | 02.09.2026 | Reissued on the current Germa-Tech technical data sheet format. New in this issue: a quick-reference card, the hardener and reducer selection gauge, the coating thickness stack, the recoat-window recovery procedure, and a product-specific troubleshooting table. Bake schedules are now stated as metal temperature. |
18WARRANTY & FURTHER INFORMATION
TALK TO US — WE MEAN ITWe are always happy to talk to customers who contact us directly. If anything on this sheet does not fit the job in front of you — an unusual substrate, a tight timeline, a cold morning, a window you have missed — call before you spray, not after.
support@amproaustralia.com · germatech.com.au This sheet is read together with the GERMA-TECH APPLICATION STANDARD (terms, conditions of application and warranty) and the Coating Thickness Guide — both hosted with the data sheets and at germatech.com.au. Warranty is conditional on correct use of the product as described on this sheet, including the sanding steps and grits in its sanding guide, within the Germa-Tech system. The information in this data sheet is given in good faith and is based on laboratory and field testing. Ampro Australia has no control over the conditions under which this product is used, so the end user must satisfy themselves that the product is suitable for the intended application and conditions. All times are quoted at 20 °C and 50% relative humidity unless stated otherwise. This sheet supersedes all previous issues.
