Summary for chromium level in stainless steel Discussion
Chromium level in stainless steel can be measured by dissolving a representative sample and analyzing the digest. In response to David L.’s question about 410 stainless with 12.4% chromium, Trevor Crichton explains that a suitable sample can be digested in hydrochloric and sulfuric acids, then brought to volume for analysis. He outlines three practical routes: oxidize the chromium to Cr6+ and compare by colorimetry, oxidize and then titrate with ferrous ammonium sulfate to a ferroin endpoint, or analyze the digest directly by ICP-OES or AAS. The answer is method-focused rather than giving a single at-home test, and it implies that laboratory wet chemistry or instrumental analysis is needed for a reliable chromium determination.
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
April 9, 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 sulphate to a ferroin endpoint 3) or, simply analyze digest directly by ICP-OES or AAS
⇦ on
or
Amazon [affil link] .
Dave Wichern
Consultant – The Bronx, New York
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
⇦ on
[affil link]
, Atomic Absorption Spectrophotometry (AAS)
⇦ on
or
Amazon [affil link] to mention but 4 techniques.
Brian Terry
Aerospace – Yeovil, Somerset, UK
Second of two simultaneous responses — April 12, 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
R&D practical scientist
Chesham, Bucks, UK
April 15, 2012