Metal bonding adhesives are used to affix certain metallic pieces together when welding is not possible or practical. However, adhesive bonding does allow for the use of joint bonding as well, in order to further improve structural integrity. Synthetic bonding with adhesives is a relatively recent development dating back to the 1930s. The first major industry, which was the aircraft construction industry, adopted metal bonding adhesives as a part of its aircraft constructing tool.
Adhesive bonding is most effectively applied on dissimilar metals with different melting points. Different melting points of dissimilar metals make welding problematic. Using this method allows for stress loads to be distributed evenly over the board rather than concentrating them on certain points. Adhesive bonding, performed in accordance to industry standards, have offered relatively reproducible bonds. Most metallic bonding adhesives work well with aluminum. Nowadays, industries around the world take advantage of a wide selection structural and non-structural strength adhesives. These adhesives have been improved both for design and manufacturing purposes. Different kinds of adhesives have been since invented, such as epoxy, acrylic, urethane-based adhesives, anaerobic adhesives, hot melt adhesives among others. Metal bonding adhesives are divided into three categories.
1- Slow Metal Bonding Adhesives
This is used for a range of panel bonding which range from, but are not limited to, body and roof panels especially back, door, van side panels to outer bed panels for trucks. Benefits of this method are that they offer guaranteed protection against corrosion, a long open time to replace large panels and maintain ideal condition of the metal in hot temperatures. Work time for this method is around 70 minutes (at room temperature of 70F, 21C degrees), which can be reduced to 35 to 40 minutes in 90F, 32C degrees. De-clamping time varies from 2.5 hours to 3 hours. The chemical process is finished and the pieces fully cured after 8 hours.
2- Medium Metal Bonding Adhesives
This method has slightly different properties than the slow metal bonding adhesives. This is also used for bonding of quarter panels, body, roof and door panels, van panels and outer bed panels for trucks. Medium metal bonding adhesive also offers corrosion protection and replaces welding altogether in certain situations. It offers a faster de-clamping of around 1.5 to 2 hours. This does, however, shorten the work time for the pieces to around 40 to 50 minutes (at 70F, 21C degrees). Full curing for this adhesive is also 8 hours.
3- Fast Metal Bonding Adhesives
Fast metal bonding adhesives are generally used to patch metal bonding and bond dissimilar metals, such as metal corners, panel sections and patch repairs for trailers made of aluminum. Like slow and medium metal bonding adhesives, fast metal bonding adhesive also guarantee corrosion protection, replaces welding and has the fastest de-clamp time of the three. Fast metal bonding adhesives fully cure in 4 hours but have a very short work time, of around 5 to 8 minutes with a de-clamp time of 20 to 30 minutes (all at 70F, 21C degrees).