How to Bond Brass
Brass is an alloy comprising zinc and copper. It is non-magnetic, resists corrosion, and is malleable. Bonding brass applications are found in a variety of industries. Applications include pipe joints, hydraulic fittings, heat exchangers, door locks and knobs, munitions, musical instruments.
Brass is readily bonded with a variety of different types of adhesives. Having so many options can make it difficult to choose. Let’s look at the options. Sometimes choosing the right adhesive for each application is done by selecting the best cure process for the application.
Anaerobic adhesives cure in the presence of metal and absence of oxygen. Brass is one of the most reactive metals so the anaerobic adhesive will set up 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.
Munitions sealing is done with UV / Anaerobic sealants. The UV light cures the surface of the adhesive, and the anaerobic mechanism cures the area hidden from the light by the brass.
Cyanoacrylate adhesives or instant adhesives are ideal for bonding brass. They are often used to bond pads to musical instruments. 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 brass 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. 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.