Surface Preperation for Adhesives

It is necessary to ensure that the substrate surfaces of the components being attached are suitably prepared. For all adhesive joints the minimum surface preparation is to clean the surfaces such that all loose substrate and grease is removed. The surfaces to be joined should be flat, some adhesives are more capable of filling spaces, but the flatter the surface the stronger the joint.

The important surface preparation routines are shown below..

Degreasing with steam, organic solvents or alkaline cleaners Mechanical methods such as blasting, brushing or grinding with emery-paper. Dipping in boiling water after etching in caustic soda. Yellow or green chromate treatment Anodising in chromic, phosphoric or sulphuric acid. Applying a suitable primer.

When using cyanoacrylate adhesives it is necessary to ensure that chlorinated solvents are not used for surface penetration. These solvents have acid stabilisers which prevent curing of the particular solvent.

Materials which are often difficult to bond and which often require enhanced surface protection include Aluminium (+alloys), Copper ( +alloys), Magnesium (+alloys), Nylon, Polyacetal, Polyethylene, Polypropylene, PTFE, PVC and Zinc. Glass also generally requires special preparation. It is often possible to greatly improve the strength of a bonded joint with difficult surfaces using an adhesive primer. In all cases the adhesive manufacturers literature should be consulted and followed to achieve the optimum bonding results.