When bonding magnets to steel structures, there are several items to consider.
Selection of Appropriate Epoxies and Adhesives
Consider the environment that the magnet or magnet assembly will be exposed to during storage and use. If the magnet or magnet assembly will be used at elevated temperatures, higher temperature adhesives and epoxies should be used. Other factors to be taken into account when selecting the appropriate bonding materials are humidity, forces the unit will be exposed to, and any other adverse condition which could contribute to a point of failure.
Substrate Surface Preparation
It is better to bond to the base magnet material than a coated or plated magnet. Coatings and platings are typically applied for their ability to curb oxidation or simply for cosmetic reasons, but not for structural integrity. Epoxies and adhesives are meant to provide structural integrity.
Nickel plating is typically very difficult to bond to. Our proprietary polymer coatings, such as PR1010 or PR1020, work well with adhesives and epoxies. However, as mentioned above, they are not designed to be structural. Where possible and permissible, it is better to strip the coating, or mask the surfaces when coating so that bonding surfaces are free of coatings. If stripping the surfaces is required, do this by lightly sandblasting or using an emery cloth or sandpaper. Make sure to clean the surfaces after etching so as to remove any loose particles that may have formed due to the process.
In all cases, cleanliness is extremely important. Even a fingerprint on the surface to be bonded can lead to potential failures when high reliability is required. This is because oils and salts from the finger transferred to the substrate materials being bonded will compromise the integrity of the bond. We do not want to introduce oils or other contaminations on the bonding surfaces prior to bonding. Touching the bonding surfaces with bare fingers introduces contamination which later compromises the integrity of the bond. Additionally, technicians must be aware of the potential for Foreign Object Damage (FOD). To avoid this potential failure point, it is important that the bonding technicians are aware of this problem and that they exercise care by handling the parts to be bonded with finger cots or gloves. It is important to extensively train and audit the assembly technicians. The technician may not realize he or she did this and would have introduced salts and oils on the bonding surfaces.
MCE extensively trains each technician involved in the bonding process. We use a variety of Standard Operating Procedures that have been tested and reviewed through years of experience. Additionally, supervisors and managers are involved in the training process to ensure any issues with the technician or training are observed, corrected, and improved upon.