Pitfalls of Using EDS in Failure Analysis

Energy Dispersive X-ray Spectroscopy (EDS) is commonly used in the course of failure analysis investigations to evaluate the elemental makeup of a material. EDS is often utilized because it provides rapid (minutes) identification of elements comprising a material, is non-destructive, and can often be performed while imaging with Scanning Electron Microscopy (SEM). EDS provides useful information and has unique capabilities including the ability to investigate small areas and perform elemental mapping, but there are limitations to using EDS. This technique should not be relied upon for quantitative analysis of material chemistry on fractured or rough surfaces, e.g. to validate conformance with a metal alloy specification. This paper evaluates the performance of EDS in comparison to other, quantitative, chemical analysis techniques such as XRF and spark-OES for four materials (low carbon steel, 308 stainless steel, brass, and aluminum), in three different surface morphologies (polished, as-cut, as-fractured). Key pitfalls of using EDS for quantitative assessment in failure analysis are identified. Metallurgists and forensic engineers alike are cautioned against using EDS results to formulate opinions based on quantitative compositional analyses using a technique not suited to do so.