Rust Analysis ―Using Infrared Raman Microscopes and Energy-Dispersive X-Ray Fluorescence Spectrometers―

User Benefits

－ Raman analysis can determine the functional groups of metallic oxides for qualitative analysis (identification) of types of rust. － Fluorescent X-ray analysis detects each element as signal peaks at different energy levels, offering a versatile tool for the evaluation of metal samples.

Introduction

Rust from metal corrosion consists of metal oxides and hydroxides that are formed by reactions between the metal, substances adhered to the metal, and air. Inorganic compounds such as metal oxides and hydroxides that contain high-mass atoms exhibit molecular vibrations in a lower frequency region than organic compounds. The analysis of these low-frequency regions by infrared spectroscopy is complex and requires beam splitters designed for far-infrared analysis and dry air or nitrogen purging. However, Raman spectroscopy can analyze these low-frequency regions using standard equipment, making it effective for the qualitative analysis of metal oxides and other inorganic compounds. Inorganic substances can also be characterized by an energy-dispersive X-ray fluorescence spectrometer (EDX). EDX works by irradiating a sample with X-rays and detecting the fluorescent X-rays produced. Because the energy of the fluorescent X-rays is unique to each element, we use them to perform qualitative analysis, including single-element substances such as metals. This approach allows EDX to be used for the qualitative analysis of single-element substances, such as metals. Raman spectroscopy irradiates the sample with a laser, measures the resulting Raman scattered light that is unique to each sample molecule and performs qualitative analysis that is based on the difference in wavelength (Raman shift) between the incident laser light and the Raman scattered light. Because Raman spectroscopy measures bonds between inorganic elements and oxygen, nitrogen, and sulfur (functional group analysis), single-element metals do not produce peaks in Raman spectra. This Application News describes an example analysis of standard metal oxides and a real-world rust sample that was performed using an AIRsight infrared Raman microscope (Fig. 1, left). An example analysis of the real-world rust sample was also performed using an EDX-8100 (Fig. 1, right).

April 2, 2024 GMT