Hi, I'm using epoxy to increase the torque strength of a joint between two lenghts of aluminium box section (currently held by a single machine screw), where lightness is critical. I'm aware that an oxide layer forms on aluminium as soon as it is exposed and that in order for the bond to be stronger I should try and apply the epoxy ASAP after having prepared the surface. At the moment I'm preparing it by sanding the aluminium with wet and dry paper to remove the oxide layer, then quickly applying epoxy and placing the other length of box section ontop and securing it with the machine screw. The joining area is only 2.25cm^2.
The way I have done is plenty strong enough for my needs, however, I tested it only 12hrs after I applied the (15 minute) epoxy and I'm worried that the bond strength may weaken over time, due to the aluminium oxide layer reforming (read this somewhere). But I can't see why this would be the case since the epoxy will prevent any oxygen reaching the aluminium. So I ask, is this even true or will the bond remain a similar strength however long I leave it? Thanks.
The way I have done is plenty strong enough for my needs, however, I tested it only 12hrs after I applied the (15 minute) epoxy and I'm worried that the bond strength may weaken over time, due to the aluminium oxide layer reforming (read this somewhere). But I can't see why this would be the case since the epoxy will prevent any oxygen reaching the aluminium. So I ask, is this even true or will the bond remain a similar strength however long I leave it? Thanks.