Moisture measurement / Osmosis
Osmosis as we often see it under polyester boats is caused by penetration of water into the gelcoat. This process has several phases.
An osmosis bladder is acidic because of the chemical reactions that occur as a result of water absorption in the gelcoat of a polyester boat. This process is known as osmosis and involves several phases:
Water absorption: Water penetrates the boat's gelcoat and is absorbed by the plastic matrix of the fibreglass hull.
Hydrolysis: Within the plastic matrix, water reacts with chemical compounds in the gelcoat and polyester resin. This reaction is known as hydrolysis and results in the formation of acids, such as acetic acid.
Formation of bladders: The acids formed and other by-products of hydrolysis can lead to the formation of small bladders or bubbles between the gelcoat and the fibreglass hull.
The presence of these acids in the bladders makes them acidic. These acids can be corrosive and damage the gelcoat and the underlying polyester, leading to delamination and the eventual phenomenon we call osmosis.
The acid in the bladders is an indicator of the damaging process taking place and can be detected during inspections of the boat. Treating osmosis usually involves removing the affected gelcoat, neutralising the acids and applying new gelcoat to prevent further damage.
If osmosis is detected, I can work with you to create a plan of action to have it treated and prevent it from recurring in the future.