In any industry that leverages stainless steel for manufacturing or within manufacturing processes, rust prevention is a top priority to ensure products or equipment are quality-made, safe, and function as intended.
The key to preventing rust is obtaining a chromium oxide-rich passivation layer on the surface of stainless steel. And to ensure that’s been achieved, stainless steel testing is an immensely helpful tool. Below we outline how we typically analyze stainless steel passivation layers for our manufacturing clients.
The Technique: Electron Spectroscopy for Chemical Analysis
Electron spectroscopy for chemical analysis (ESCA), which is also called X-Ray Photoelectron Spectroscopy (XPS), uses an x-ray beam to excite atoms on the surface of a solid sample, which results in the emission of photoelectrons.
This makes ESCA an ideal technique for analyzing stainless steel passivation layers because it not only provides a quantitative measurement of any surface impurities in the oxide layer, but also information on the oxidation state of chromium and iron, too.
During our analysis, we were looking to identify the chromium to iron ratios within a sample. Bulk steel will typically have chromium to iron ratios of around 0.3, and a well passivated stainless steel surface will have a ratio of around 2.0. This ratio is a key indicator as to the degree of passivation on the surface of the stainless steel device.
The figure below shows a survey scan of the surface of a passivated stainless steel sample.
Going deeper with our analysis, the figures high-resolution scans of chromium (Cr2p3; top) and iron (Fe2p3; bottom) of a passivated stainless steel surface. In this case, the chromium-to-iron ratio is 2.4.
What does this tell us? Based on the chemical composition of the sample, we know it’s up to par with scientific requirements to prevent rust.
In Need of a Stainless Steel Testing Partner?
Innovatech Labs can be a trusted partner to deliver fast, accurate stainless steel testing results at an affordable price.
In addition, measuring the passivation layer on stainless steel is just one of the many services we provide to help our manufacturing customers maintain quality in their manufacturing processes.