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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 improve cured epoxy’s moisture exclusion effectiveness further. 422 is used as a barrier coating additive to help prevent gelcoat blistering in polyester fiberglass 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


422 Barrier Coat Additive


Create an abrasion and moisture-resistant surface in:

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


  • Color | Light Gray
  • Cures to Gray


  • 16 oz of 422 will modify up to 0.5 gal of mixed epoxy
    • 15-20% by volume (3 tbsp) | 8 fl oz epoxy

Product Size:

  • 422 | 16 oz



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.

Fiberglass Repairs

Recently we revised our most popular instruction manual, Fiberglass Boat Repair & Maintenance, bringing it up to date and expanding it to 146 pages. It contains the very latest fiberglass 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