On the surface

What is that stuff on the surface? Where did it come from? Does it match this material? These are common questions asked of a scientist who specializes in the examination of a sample surface. A surface analyst has many techniques to choose from in order to solve the particular problem at hand. To those unfamiliar with this discipline, the variety of surface analytical instrumentation, coupled with terminology full of acronyms and jargon can be confusing. Despite the complexity of the techniques, the answers that surface analysis give can be easily understood and useful to a wide variety of people.

The term "surface analysis" generally refers to examination of the outermost sample monolayers. Examples of this would be observing surface structure uniformity to see microscopic imperfections, like bubbles, cracks, voids, or inclusions; or analysis of contaminants, like a thin layer of oil that prohibits adhesion of phosphate treatment to a steel surface. In addition, the sample can be prepared in cross section to allow analysis at various depths. The photograph shown below is an electron microscope cross section image of a metal desk drawer handle that broke during shipment.

Analysis revealed that the handle was a zinc casting covered with a copper flash, seven layers of nickel and a chromium top coat for a total surface treatment only 12 microns thick (about one fifth the thickness of the average human hair). Along the same lines, for a painted object one can determine the number of paint layers and type of paint in each layer. The presence of metal treatments such as phosphate coatings, galvanizing, and plating can be confirmed and the adhesion between the layers observed.

Surface analytical techniques are used to examine many materials including metals, alloys, glass, polymers, rubber, cloth, lubricants, etc. Samples originate from sources such as mechanical equipment, fire debris, clothing, electrical components, medical devices, vehicles (land, water, or air), buildings etc. Common applications include the analysis of material transfer from vehicular accidents or machinery failure. This may involve chemical comparison of small samples of paint, plastic, rubber or metal. Broken equipment can be analyzed to determine the cause of failure as evidenced by observation of abrasion, cracking, corrosion, or impact. Chemical analysis of recycled materials may identify impurities that affect product performance. Product identification, validation of a material composition, patent infringement, chemical identification, and detection of impurities are other common assignments for a surface analyst.

The variety of surface analytical techniques is extensive and applications for the use of surface analysis are seemingly endless. Upcoming issues of Unified News will include articles that focus on specific techniques. Contact Lori Streit for further information or to discuss any questions you may have.