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Posted By ASC, Monday, July 10, 2017

BLOG:  “As Received” and Adhesive Performance
By Jim Swope, Expert Blogger (The ChemQuest Group, Inc.)

In my early days as a supplier of adhesives to automotive assembly operations, I dreaded the words “as received” on a specification because its implied meaning could affect adhesive performance (light mill oil commonly used as a rust preventative by parts suppliers is often the culprit).

Mill oils may not present major problems in assemblies where the adhesive process is augmented by mechanical methods such as spot welds or the adhesive process displaces the oil. However, when the adhesive is carrying the full load (no mechanical augmentation) or the operating conditions are extreme, surface contamination will present issues. A clean surface is commonly understood as being critical to repeated success in bonding. Sometimes the parts supplier would insist their parts are cleaned prior to shipping but further probing would reveal they added a rust preventative in the final rinse or as a subsequent process. The presence of a rust preventative can retard or arrest chemical cures or act as a barrier to proper wetting of the surface.The outcome of which is classic weak link theory: The assembly fails due to weakening of a critical component – the adhesive interface to the substrate.

What steps can be taken to assure that we avoid failure in critical assemblies? How do we balance that against cost pressures? Who bears the cost burden of proper surface preparation?

The answer lies with the specification writer who ought to own not only the bonding specification but the condition of the substrates that are critical to the assembly... Read More


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