The following procedures are common to the majority of repair or building projects – on the boat or in the home and regardless of the type of structure or material on which work is being carried out. Whether bonding, fairing or applying fabrics, the success of the application depends not only on the strength of the epoxy but also on how well the epoxy adheres to the surface to which it is being applied. Unless bonding to partially cured epoxy, the strength of the bond relies on the ability of the epoxy to mechanically “key” into the surface. Thus, the following three steps of surface preparation are a critical part of any secondary bonding operation. For good adhesion, bonding surfaces must be:

1. Clean Bonding surfaces must be free of any contaminants such as grease, oil, wax or mould release. Clean contaminated surfaces with WEST SYSTEM 850 Solvent. (Figure 6). Wipe the surface with fresh paper towels before the solvent dries. Clean surfaces before sanding to avoid abrading the contaminant into the surface. Follow all safety precautions when working with solvents.

2. Dry All bonding surfaces must be as dry as possible for good adhesion. If necessary, accelerate drying by warming the bonding surface with a hot air gun, hair dryer or heat lamp (Figure 7). Use fans to move the air in confined or enclosed spaces. Be careful of condensation when working outdoors or whenever the temperature of the work environment changes.

3. Sanded Thoroughly abrade hardwoods and non-porous surfaces with 80-grit aluminium oxide paper to provide a good mechanical “key” for the epoxy (Figure 8). Ensure the surface to be bonded is solid. Remove any flaking, chalking, blistering or old coating before sanding. Remove all dust after sanding.

The importance of the three operations detailed above cannot be stressed too strongly – for high strength, durable bonds, surfaces must be clean, dry and thoroughly abraded after removing previous surface coatings.