Whether you are bonding, fairing or applying fabrics, thorough surface preparation is key to the success of the application and end result.
Epoxy strength and adhesive properties are very important to a successful project but so too is proper surface preparation.
For high strength, durable bonds, surfaces must be clean, dry and thoroughly abraded removing previous surface coatings. This is because the strength of the bond relies on the ability of the epoxy to mechanically ‘key’ into the surface, unless you are bonding to partially cured epoxy.
This page covers:
Three-step surface preparation for good adhesion
Special preparation techniques for different materials
Tip for first-time users: conduct an adhesion test
The following three steps of surface preparation are a critical part of any secondary bonding operation.
Bonding surfaces must be free of any contaminants such as grease, oil, wax or mould release. Clean contaminated surfaces with a solvent then wipe the surface with fresh paper towels before the solvent dries. Before you start sanding, clean surfaces to avoid abrading the contaminant into the surface.
Clean the surface. Use a solvent if necessary to remove all contaminates.
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. Use fans to move the air around in confined or enclosed spaces. If you are working outdoors, be sure to guard against condensation. Take particular care whenever the temperature of the work environment changes.
Dry the surface. Allow the surface to dry thoroughly or use heat or a fan to speed drying.
Thoroughly abrade hardwoods and non-porous surfaces with 80-grit aluminium oxide paper to provide a good mechanical ‘key’ for the epoxy. Ensure that the surface to be bonded is solid. Remove any flaking, chalking, blistering or old coating before you start sanding. Remove all dust after you have finished sanding.
Sand non-porous surfaces. Provide a texture for epoxy to key into.
Some surfaces require extra preparation or particular care before moving on to the next stage, like bonding or fairing. This table contains surface preparation guidance for various metals, woods and other miscellaneous materials.
When you are looking to bond any type of material, it is a good idea to conduct an adhesion test first to check the surface is properly prepared. That way you can be sure that the adhesive will work on your real project.