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How to test the chromium level in stainless steel? i.e., 12.4% chromium 410 SS





April 9, 2012

Q. Is there a way to test the chromium levels in stainless steel? i.e 12.4% chromium 410 SS

David L
- North Billerica, Massachusetts



First of two simultaneous responses -- April 11, 2012

A. Sure. Dissolve a suitable sample, say 500 mg, in a mixture of HCl and H2SO4. Heat the finished digest to the fume point, then cool and make up to some convenient volume.

You may then determine Cr by: 1) Oxidize an aliquot of digest up to Cr6+ with KMnO4, get rid of excess oxidant with NaN3, then compare to suitable standards via colorimetry 2) Oxidize digest up to Cr6+ with sodium peroxide, adjust pH to about 9 with aqua ammonia, filter off Fe(OH)3, acidify again, then titrate with ferrous ammonium sulfate to a ferroin endpoint 3) or, simply analyze digest directly by ICP-OES or AAS.

dave wichern
Dave Wichern
Consultant - The Bronx, New York



Second of two simultaneous responses -- April 12, 2012

A. Hi David,

Question is rather abstract, so we the readers do not know whether you are trying to distinguish one material from another or whether you are trying to separate out batches of the same material based on their individual batch chemistries, so this answer is going to be a bit generalised.

Possibilities are: X-Ray Fluorescence (XRF), Energy Dispersive X-Ray (EDX) attached to a Scanning Electron Microscope (SEM), Ion-Coupled Plasma (ICP) spectroscopy, Atomic Absorption Spectrophotometry (AAS) to mention but 4 techniques.

Brian Terry
Aerospace - Yeovil, Somerset, UK



April 15, 2012

A. Chromium levels in stainless steels are given in a range because the composition for any particular alloy is not precise. I therefore suggest using EDX and analyse the whole samples. This will help you identify the full range of metals present and hence what alloy it really is. EDX is easy to use, but you do need an SEM.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK


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