Bonding & sealing

Sealant is the right choice when a joint needs to be sealed and movement/vibration must be absorbed (e.g., deck fittings, hatches, window frames, penetrations). Adhesive is the right choice when a permanent bond is required (e.g., brackets, trim, repair parts). Often, the choice is between “elastic sealing” and “structural bonding.” The decisive factors are the substrate (FRP, aluminum, stainless steel, wood), UV exposure, and whether the assembly will need to be disassembled later.

Most problems arise from inadequate preparation. Standard procedure: clean/degrease (using a suitable cleaner), sand (if required), remove dust, then apply primer/activator as per the manufacturer’s instructions if necessary. On deck, it is also important to completely remove old sealant, keep contact surfaces dry, and avoid sealing “over” dirt or salt.

This depends on the product, temperature, humidity, and layer thickness. One-component sealants usually cure from the outside in; thick beads take significantly longer. Rule of thumb: do not subject to full mechanical stress or permanent water/underwater exposure until fully cured. Follow the manufacturer’s instructions regarding skin formation, hand strength, and full cure.

1K is ideal for classic sealing jobs and many bonding applications because it is easy to apply and accommodates movement well. 2K (e.g., epoxy) is suitable for high-strength bonding, gap filling, and repairs (fiberglass/metal) when high strength is required or when a defined cure is desired regardless of humidity. For 2K: mix correctly, use the appropriate mixing tip, and observe the processing time (pot life).

Deck fittings/windows/hatches: elastic sealant + proper primer strategy (if necessary). Cracks/chipping/minor repairs: epoxy/two-component repair solutions. Metal repair/emergency: “liquid metal”/epoxy can help, but is not a permanent solution for safety-critical components. Bonding strips/brackets: depending on the load and whether disassembly is desired, use either an elastic adhesive/sealant or a structural adhesive.

Contact surfaces must be dry, clean, and free of grease. Do not “flatten” the sealant: a defined sealing layer is important (use spacers or washers if necessary). Tighten screws evenly and—depending on the system—check them after a short time. Mask off, smooth cleanly, and remove excess material before it fully cures. For penetrations/screw holes: Chamfer the edges and work the sealant in as a barrier.

Perform regular visual inspections (cracks, delamination, yellowing), remove salt/dirt, and avoid mechanical stress (abrasion). In areas with high UV exposure, use UV-resistant products or provide protection (covering/paint after system approval). If joints come loose or water seeps in, replace them promptly—small leaks can quickly lead to major damage on board.