Ferro Cement

[Guest]

A ferro cement hull built in 1980 was dried out in Venezuela and three coats of epoxy tar applied to the bare substrate in 1999. The paint has been bubbling off in a manner similar to osmotic pressure and the bubbling is prevalent around the waterline. The epoxy tar is very well adhered to the substrate. Suggestions to recoat have been with a cementicous coating or a moisture cured urethane. Antifouling paint does not bubble off the substrate. Have been advised that uncured amine used in the epoxy hardener is delequescent and will therefore form a path for water to permeate to below the epoxy, hence osmotic pressure. Has any reader experienced the same or similar problems and what was the cure? All advice welcome.

 

[Jules]

My Dad built a ferro ketch and launched in 1985, same osmotic bubbling occurred. Sorry I can't be much help, as I can't remember exactly what we did, but the solution came from West Systems, then based in Southampton. Whatever they gave us was superb! Suggest a search under "Epoxy" or suchlike.