and sailboat maintenance
Go to any chandlery
or marine store and you’ll be faced with a multitude of marine sealants
and caulking materials. In this short article we’ll try and sort
them out into some sort of order so you can select the right sealant
for each job on your boat.
Essentially, every marine sealant is one of just three products – polysulfide, polyurethane or silicon.
Polysulfide - the "workhorse"
Polysulfide is a synthetic rubber compound and is the “workhorse” of marine sealants. A polysulfide sealant will adhere to joint materials well, but will allow for movement due to temperature or load. It will attack plastics (but not Marelon, epoxy or Delrin). It’s sometimes sold under the trade name “Thiokol”. It can be sanded and painted after it cures (typically 14-21 days). It can be used below the waterline and is good for thru-hull fittings and fixing deck hardware.
Two part polysulfide sealant is used to caulk teak decks.
Polyurethane - the adhesive
Polyurethane is the sealant to use where you’re looking for a permanent seal. It’s an adhesive more than a sealant. Don’t use it if you think you may want to pull the joint apart in the future. Don’t use it on plastics as it will attack polycarbonate, acrylic, ABS and PVC (but not Marelon, epoxy or Delrin ). It can be used below the waterline and is good for hull-deck joints and thru-hull fittings.
adhesive/sealant 5200 by 3M
Silicone - the gasket
Silicone is a gasket material, not a sealant. Its adhesive properties are minimal and should be disregarded. It is great for insulating dissimilar metals such as stainless steel and aluminum and for any above the waterline joint that needs to be dismantled periodically. It is not possible to paint silicone. Up until recently it was the only material you could use to bed plastic (portlights etc.)
silicone rubber sealant by BoatLife
Silicone/polyurethane - the hybrid
There is now a fourth product, a silicon/polyurethane hybrid that combines the adhesive properties of polyurethane with the gasket qualities of silicone. It is now the sealant of choice for sealing plastic components above the waterline.
So to select the right sealant for your job, you need to answer just three questions
Unfortunately although we believe all the products mentioned above are of professional marine quality, we cannot make any specific recommendations on which particular sealant brand you should use in any particular situation.
Make sure you read the technical brochures available on the internet for any sealant you intend to use, and pay particular attention to any specific cleaning and priming requirements mentioned in the technical literature.
Copyright 2011 sailingmates.com