The Adhesive Bonding of Stainless Steel
Stainless Steel can be bonded with adhesive in order to achieve properties which cannot be obtained through other connection technologies however, it is important to bear in mind that not all stainless steel applications are suitable for adhesive bonding.
What Components are involved in Adhesive Bonding?
Firstly it is important to note that the larger the adhesive surface the greater the transmitted forces are. When crimping or fixing with screws or rivets enhances the strength of the adhesive bond and when repairs are carried out now they usually involve making adhesive bonds using hybrid connections with welding and rivets.
In a permanently moist environment it is important to notice that although many stainless steel adhesives are corrosion resistant when subjected to moisture over time the adhesive strength may well be reduced because of this moisture infiltration.
How is Stainless Steel Prepared for Adhesive Bonding?
In relation to preparing stainless steel for adhesive bonding it is important that its surface is clean. Clean surfaces guarantee adhesive over the long term and thus you must ensure the surface of the stainless steel is completely free from any dust, grease or oil and this can easily be achieved by steam cleaning the stainless steel or using an ultrasonic cleaning bath for anything small in size.
There are a number of new technologies which are becoming popular and these are:
- Thermal activation (pre-treatment method)
- Plasma technologies (post-treatment method)
- Laser Technologies (post-treatment method)
Which Adhesive Systems are appropriate for bonding Stainless Steel?
Selection of the adhesive is obviously key and it needs to be right. There are a number of questions which need to be asked in order to effectively determine which adhesive will be most suited. One of the questions is whether cold or hot curing adhesives based on epoxy resin or polyurethane should be used?
Epoxy resin adhesives have an extremely high cohesive strength. in addition to this they are very resistant to the influences of various factors which could in other cases have an effect. At around 150 to 200 degrees the connection will lose some of its strength although it doesn’t decompose chemically. This is great because once it has cooled the epoxy resins regain their original strength.
Two component structural adhesives are suitable for materials which are subjected to greater stress. If you have completely overlapping components such as signs then to successfully bond these then you should use or rather we recommend double-sided adhesive tapes.
How do you Test an Adhesive Bond?
In order to test an adhesive bond then you need to carry out what is known as an adhesive trial. It is advisable to perform a destructive test in the form of quasi-static tensile tests. The connection strength can be set in relation to the theoretical strength of the adhesive.
Furthermore the mode of failure of the fracture will serve as criterion for the quality of the connection and the adhesive bond created. The aim of such testing is to obtain fractures within the adhesive layer and then these fractures will then indicate that the surface wouldn’t have been previously treated.