How to Bond Copper
Copper and its alloys are readily bonded with a variety of adhesive types. Adhesives are preferred over soldering as they do not heat damage the copper.
Anaerobic adhesives cure in the presence of metal and absence of oxygen. Copper is one of the most reactive metals, so the anaerobic adhesive will set up and cure much more quickly than the time listed for fixture speed on steel.
Anaerobics are used for threadlocking, thread sealing, form in place gaskets, weld sealing, retaining and munitions sealing.
For threadlocking, permanent and removable grades are available in a variety of viscosities (from wicking grades to high viscosity grades. Specialty products for use with potable water are also available. Product selection can be done based on the strength and gap (or bolt size).
Thread sealants are also available for sealing threaded pipe connections. Specialty grades for hydraulics contain no fillers which could cause blockages. Grades for use with oxygen, potable water grades, and UL Classified grades are also used in sealing brass piping.
For form-in-place gasketing consider Permabond LH197 is flexible and easier to remove from soft metals.
Retaining compound product selection is heavily based on gap fill requirement. Retaining compounds are used to permanently bond brass co-axial non-threaded joints.
Cyanoacrylate adhesives or instant adhesives are ideal for bonding copper. The highest strength bonds are created with methyl cyanoacrylates such as the original Permabond 910. Although very high strength bonds are formed with cyanoacrylate adhesives, structural adhesives may be needed if you are bonding copper and require resistance to polar solvents or impact.
Structural adhesives – structural adhesives are defined as adhesives that form bonds that bear a structural load. Examples include structural acrylic adhesive and epoxies.
All grades bond well so choosing can be done based on the type of cure method that is preferable to your application. Single component epoxies cure with heat. Two component epoxies are mixed. Epoxies are commonly used to pot tubing in heat exchangers.
There are several types of structural acrylics. Surface activated acrylics cure by applying a water thin initiator to one surface and the resin to the other
Surface activated acrylics – cure begins after joining the two components where a water thin initiator has been applied to one surface and the resin to the other.
Bead on Bead acrylics – A bead of one part is dispensed onto a bead of the other. Sufficient mixing of the two components occurs when the components are joined, and the adhesive squeezed into a thin bond line.