B. A. Miller, IMR Metallurgical Services, Louisville, KY
Analysis of corrosion products is an indispensable tool for the failure analyst, providing clues to the cause of degradation. Unfortunately, corrosion evidence can be contaminated by a wide variety of substances. Ingress of contamination often occurs after corrosion has perforated the component. Additional contamination sources including; cleaning, repair attempts, handling, non-destructive examination fluids, and cutting materials. Even sampling of corrosion product for instrumental analysis can introduce foreign materials that complicate the analysis process, even to the point of rendering the analysis results of little value.
This paper will explore typical practices for corrosion sampling, trying to avoid extraneous contamination. Some of the possible sources of inadvertent contaminant introduction will be illustrated by failure analysis case studies. Cases with different levels of corrosion product integrity will be discussed.
Identification of substances responsible for corrosion failures is necessary for determining actions to prevent recurrence. Obtaining unaltered corrosion product for instrumental analysis is often problematic, as foreign substances are often intentionally or inadvertently introduced. The purpose of this presentation is to address corrosion evidence preservation from the failure analyst’s perspective.
