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422 Barrier Coat Additive

While WEST SYSTEM Epoxy creates an excellent moisture barrier by itself, 422 Barrier Coat Additive is a proprietary blend designed to further improve cured epoxy’s moisture exclusion effectiveness. 422 is used as a barrier coating additive to help prevent gelcoat blistering in polyester fibreglass boats. 422 also increases the epoxy’s abrasion resistance. Add to any mixed WEST SYSTEM 105/200 Series Hardener combination.

Designed for:

  • Moisture Resistance
  • Abrasion Resistance
  • Preventing Gelcoat Blistering


WEST SYSTEM| image: Amazon Product Listing Photos (11)


Create an abrasion and moisture-resistant surface in:

  • Fibreglass Repairs
  • Gelcoat Blister Repairs
  • Boat Restoration
  • Rudder Restoration
  • Moisture Exclusion


  • Colour | Light Grey
  • Cures to Grey


Add 20% to 25% by weight of 422 to the mixed epoxy.


  • 422 | 0.5kg
  • 422B | 3.0kg



Modifying with fillers and additives makes WEST SYSTEM epoxy extremely versatile for a wide variety of bonding and coating applications. Epoxy can be thickened to the ideal consistency needed for a particular job. Epoxy thickened with adhesive (high-density) fillers strengthens structural bonds, bridges gaps, and fills voids. Epoxy thickened with fairing (low-density) fillers is easily sanded and shaped after it cures.

Fibreglass Repairs

Recently we revised our most popular instruction manual, Fibreglass Boat Repair & Maintenance, bringing it up to date and expanding it to 146 pages. It contains the very latest fibreglass repair techniques and features complete sections devoted to repairing cracks, holes, damaged skins, cores, keels, and rudders, installing hardware, installing teak veneer decks, gelcoat blister repair and prevention, and final fairing and finishing.

Using WEST SYSTEMFillers & Additives