Those annoying polyester booties? That is not rust. That is osmosis.
Osmosis is a physical process that can occur, for example, in the polyester laminate of boats, polyester garden tables, polyester tubs, suitcases, Alpines, Bonitos and Corvettes.
But most people are familiar with the pleasure boat industry phenomenon. By water. And due to the fact that gelcoat and polyester are not always watertight.
In the manufacturing process, the fiber is impregnated with polyester resin, creating a so-called laminate. Small air inclusions may remain in the laminate during this process. Osmosis occurs when moisture penetrates the laminate through the microscopic openings in the gel coat (the smooth finishing layer), whereby this moisture then mixes with the chemical components present in the polyester laminate and a fluid flow starts.
A vapor formation also occurs which presses the gel coat on expansion. And that causes those scary vesicles ... Those vesicles are filled with the result of a chemical reaction. The water that there coming out is sour.
A repair consists of opening the bladders, possibly filling them, and then applying a watertight barrier, as a result of which water can no longer enter the laminate.
- You open all the bladders, with a sander, scraper, countersink, etc.
- You rinse the bladders thoroughly with fresh water and let them dry well.
- When the polyester is dry, sand it roughly and apply epoxy filler.
- You can then sand it lightly and finish with your current paint system.
- And then sealing that paint with a good wax is very important to guarantee the 'watertightness' of the polyester, the gelcoat and the paint.
Always wear respiratory protection when sanding to the polyester.
