BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI - Universitatea ...

BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI
Publicat de
Universitatea Tehnică „Gheorghe Asachi” din Iaşi
Tomul LVI (LX), Fasc. 2, 2010
Secţia
CONSTRUCŢII DE MAŞINI
ADHESIVE BONDING OF SURFACE TREATED ALUMINIUM
BY
BIRGIT KJÆRSIDE STORM
Abstract. Adhesive Bonding of aluminium and aluminium alloys can be carried
out so a strong bonding is the result. The perfect bonding between two aluminium
parts will be a bonding, where the material will break in the aluminium part, because
in that case the bonding is stronger than the aluminium. For making a strong bonding
a structural adhesive shall be used. A structural adhesive can be made of epoxy,
polyurethane, acrylate, cyanoacrylate and a few other types. In some cases an
anaerobe adhesive can cure up with aluminium. There is interaction between the
adhesive, the aluminium alloy and the surface treatment. Aluminium creates in
atmospheric air immediately an oxide layer on the surface. Anodized aluminium
reacts with contaminations and CO2, which gives a surface with a low surface tension,
though aluminium will have a high surface tension. The low surface tension of the
reacted surface cause a bad wetting of the surface with the adhesive, and an
insufficient wetting causes bad adhesion between the aluminium and the adhesive. For
making a good bonding a good wetting is necessary. The sufficient wetting can be
made on the aluminium by making a surface treatment. The surface treatment can be
an anodizing. For obtaining the best adhesion on anodized surface the adhesive shall
be carried out before the sealing immediately after the anodizing. The fresh anodized
aluminium has a bigger surface and open pores, which cause a mechanical bonding in
addition to the adhesion. The non sealed aluminium has reactive groups, which in
some cases can react with reactive groups in the adhesive and can cause a chemical
bonding as well. The non-sealed anodized aluminium can be treated with a primer,
which can react with the active groups and can run into the pores and fill out the
porousity. Before the primer has cured up totally the adhesive shall be added to the
system for making a chemical reaction between the primer and the adhesive. Using
such a system can give a higher strength in the bonding.
Key words: aluminium, anodizing, adhesive, adhesive bonding, surface
treatment, wetting
1. Introduction
Adhesive Bonding of aluminium and aluminium alloys can be carried out so
a strong bonding is the result. The perfect bonding between two aluminium