Osmosis Damage in Polyester / Glass Fibre Reinforced Plastic

„Real“ osmosis is to be understood as contact surface blisters formed between the gel coat and laminate, or within the laminate, containing a liquid which is reactive to acids.

In assessing the extent of the damage the following factors are important:

  • Quantity, size, local distribution and pattern of the blisters.
  • Affected areas (as a percentage), delamination, and whether mechanical stability is still ensured.

The following have come to be recognised as causes of „real“ osmosis:

  • Gel coat is too thin or microporous, or too highly filled
  • Air voids
  • Insufficient hardening or preparation
  • Hydrolysis
  • Ageing
  • Natural diffusion of water
  • Damage due to chlorinated hydrocarbons such as methylene chloride, dichloromethane and trichloroethane.

The product labelling will indicate whether any of the substances mentioned above, which would be damaging to GFRP materials, are contained in the product. To avoid a re-occurrence of “real” osmosis, yachts and boats, whether new or in use, should be preserved with a preventative coating of epoxy primer of the recommended film thickness.

System 8 - Treatment of Osmosis

B = brush / LS = air-spraying / R = roller / AS = airless-spraying