Home › Forums › Wooden Boat Building › Marine Sealant Types Explained
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February 17, 2021 at 10:47 am #12972fallertonParticipant
Here is a helpful summary of applications for various marine sealant types:
Reprinted from “Common Sealant Types Explained”, article in Jamestown Distributors Email Newsletter, issued February 17, 2021.
The terms ‘marine caulk’ and ‘marine sealant’ are often used interchangeably in boating circles. The majority of marine-specific sealants are one of three material types: Polysulfide, Polyurethane, and Silicone. Understanding the differences will help you choose the right sealant for your project!
Polyurethane adhesives form an extremely strong bond while retaining flexibility and strength above or below the waterline. Polyurethanes are ideal for thru-hull fastening, and the best choice for hull-to-deck joints, deck fittings, railings and transducers. They bond tenaciously to fiberglass, wood, metal, and glass.
Elastomeric sealants create a waterproof seal that make them a good option for stopping leaks, sealing portholes, and bedding hardware and windshields. They are generally compatible with plastics and Plexiglass, fiberglass, wood, glass, and metal surfaces, but should not be used on deck seams. They cure fast, have high UV stability, and are paintable and stain resistant. And, because it’s not a permanent adhesive, you can disassemble components if necessary. Because they are intended for bedding and sealing, they lack the bond strength of polyurethanes.
Polysulfide caulks are flexible adhesive compounds used above and below the waterline. They are ideal for teak decks, bedding deck and hull hardware, sealing thru-hull fittings, and underwater seams. They bond to fiberglass, wood, metal, glass, and themselves. Polysulfides exhibit excellent resistance to teak oils, gasoline, and diesel fuel. Note: Polysulfides contain solvents that can damage ABS, PVC, acrylic and polycarbonate plastic surfaces.
Marine Silicone sealants are mildew resistant, non-sagging, moisture curing products, suitable for above the waterline applications only. Examples include head plumbing, interior & exterior wood, trim sealing and as a gasket adhesive. Do not use silicone sealants to bed or install glass, acrylic, or polycarbonate windows that are not also mechanically fastened, or on any surface to be painted.
Teak deck caulks are typically one-part, neutral curing, adhesive sealants specially formulated for caulking teak decks with outstanding adhesion to teak and other naturally oily woods. They cure to form a tough, flexible, solid rubber seal with excellent temperature stability and resistance to chemicals, sunlight, UV and water. Upon full cure, it can even be sanded flush. Note: Cure can take up to two weeks. Do not use for applications outside of caulking teak deck seams.
February 27, 2021 at 9:42 am #12973Marty CalonParticipantNice summary, thank you!
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