ADINOX® M425 — Primerless Structural MMA for Galvanized Steel

ADINOX® M425 is a two-part toughened structural adhesive engineered for high-performance bonding of metals — including galvanized steel — thermoset and thermoplastic substrates, and composite materials. Its 10:1 mix ratio delivers ultrafast structural strength development with a thixotropic, non-sagging formulation that fills gaps up to 6 mm (0.24 in).

M425 bonds aluminum, stainless steel, carbon steel, galvanized steel, fiberglass (FRP), carbon fiber, ABS, polycarbonate, nylon, and most engineering plastics — all without primer. With an open time of 2–4 minutes and handling strength in 10–15 minutes at room temperature, it enables efficient production cycles with minimal fixturing.

The toughened MMA formulation provides high impact resistance, excellent thermal cycling durability, and quantifiable chemical resistance to fuels, solvents, lubricants, and aqueous media. Black color cured — ideal for industrial assemblies where bond lines are not visible.

Property	Value
Chemistry	Methyl Methacrylate (MMA), two-component
Mix Ratio	10:1 by volume (9:1 by weight)
Color (mixed/cured)	Black
Viscosity (Resin A)	190,000–340,000 cP
Open Time	2–4 min @ 77°F (25°C)
Handling Strength	10–15 min @ 77°F (25°C)
Full Cure	24 hours @ 77°F (25°C)
Gap Fill	Up to 0.24 in (6 mm)
Elongation (ASTM D 638)	30%
Tensile Strength (ASTM D 638)	3,191–3,481 PSI (22–24 MPa)
Modulus (ASTM D 638)	128,000–195,000 PSI (883–1,344 MPa)
Lap Shear — SS/SS (ASTM D 1002)	>3,046 PSI (>21 MPa) — Cohesive failure
Lap Shear — Al/Al (ASTM D 1002)	>3,191 PSI (>22 MPa) — Cohesive failure
Lap Shear — Galv/Galv (ASTM D 1002)	>2,756 PSI (>19 MPa) — Substrate failure
Impact Resistance (ASTM D 256)	21 ft·lb/in (1,121 J/m)
Hardness (Shore D)	70
Service Temperature	-40 to 250°F (-40 to 121°C)

Medium	Retained Strength
Gasoline	>3,046 PSI (>21 MPa)
Acetic Acid 10%	>3,046 PSI (>21 MPa)
Xylene	>3,046 PSI (>21 MPa)
Lubricating Oil HD-30	>3,191 PSI (>22 MPa)
Paraffin	>2,901 PSI (>20 MPa)
Water @ 73°F (23°C)	>3,046 PSI (>21 MPa)
Water @ 194°F (90°C)	>2,901 PSI (>20 MPa)

1. Surface Preparation

Clean surfaces with isopropyl alcohol or acetone. Remove rust or mill scale by abrasion before solvent cleaning. Light sanding improves wetting and joint strength. Most metals, including galvanized steel, bond directly after solvent wipe without primer.

2. Prepare the Cartridge

Purge the dual cartridge before and after attaching the 10:1 static mixing nozzle until a uniform black color is achieved. For aged cartridges, cure a small purged amount to confirm reactivity.

3. Apply the Adhesive

Dispense enough adhesive to completely fill the bond gap. Plan for controlled squeeze-out at joint edges. M425 fills gaps up to 6 mm without sagging.

4. Assemble and Fixture

Position parts and clamp firmly. Repositioning is possible within the 2–4 minute open time. Check hardness at joint edges before releasing fixtures. Handling strength develops in 10–15 minutes at 77°F.

5. Full Cure

Allow 24 hours at room temperature for full mechanical properties. Below 65°F cure slows; above 85°F it accelerates and shortens open time.

Can ADINOX M425 bond galvanized steel?

Yes. M425 is one of the few structural MMA adhesives that bonds galvanized steel directly without primer. Lap shear on galvanized-to-galvanized substrates exceeds 2,756 PSI — failure occurs in the zinc coating, not the adhesive.

Does M425 require a primer for metals?

No. M425 achieves full structural strength on aluminum, stainless steel, carbon steel, and galvanized steel with a simple solvent wipe and optional light sanding. No primer or activator is needed.

What is the difference between M425 and M422?

M425 is black, bonds galvanized steel, has higher modulus (128,000–195,000 PSI vs 77,000–98,000), and shorter open time (2–4 min vs 4–6 min). M422 is gray, has higher elongation (≥100% vs 30%), and is optimized for visible bond lines on stainless steel and aluminum.

How fast does M425 cure?

Open time 2–4 minutes, handling strength 10–15 minutes, full cure 24 hours at 77°F (25°C). M425 has the fastest open time in the ADINOX 10:1 MMA range.

What substrates can M425 bond?

Aluminum (all series including 7000), stainless steel, carbon steel, galvanized steel, anodized aluminum, fiberglass (FRP), carbon fiber, ABS, polycarbonate, acrylic (PMMA), nylon, PBT, PVC, polystyrene, polyurethane, phenolics, gel coats, and PPO. Not suitable for PE, PP, or PTFE.

What chemicals can M425 resist?

After 30-day immersion testing (ASTM D 1002), M425 retains over 90% lap shear strength against gasoline, xylene, lubricating oil, acetic acid, paraffin, and water at both ambient and 194°F temperatures.

Can M425 replace welding for structural metal joints?

In many structural assemblies, M425 can replace or supplement welding — especially on galvanized steel, thin-gauge metals, and dissimilar material joints where welding would damage coatings or cause distortion. The adhesive distributes stress across the bond area rather than concentrating it at weld points.

What dispensing equipment is needed?

Standard 10:1 dual cartridges (50 ml, 250 ml, 490 ml) with manual or pneumatic applicator gun and static mixing nozzle. For automated systems, use PTFE or UHMW polyethylene seals. Avoid copper, zinc, or brass in internal equipment components.

What is the gap-filling capacity of M425?

M425 fills gaps up to 6 mm (0.24 in) without sagging. Its thixotropic formulation holds position on vertical and overhead surfaces during the cure cycle.