Metal finishing Q&As since 1989
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17-4 SS Free Iron Test - Prefabrication?
Q. Is it possible to identify or test for contaminated 17-4 SS prior to fabrication?
We utilize a copper sulphate [on
eBay or
Amazon]test to identify free iron on post-manufactured product. However when test results are positive for free iron we would like to be able to identify contaminated material prior to fabrication.
Will 17-4 SS exhibit a "false" free iron indication if tested prior to heat treatment?
QM - T.C., Michigan
August 5, 2009
First of two simultaneous responses --
A. I do not think that the heat treat will affect the test, but the handling it with steel fork lifts or tongs might. Try your test on several parts before heat treat to see.
James Watts- Navarre, Florida
August 6, 2009
Second of two simultaneous responses --
A. No matter what the heat treatment condition, no matter if it is still as-cast and has received no heat treatment at all, a positive free-iron test indicates surface contamination.
Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.
August 7, 2009
A. When you say "Post Manufacture" are you including a Passivation step? If not, you need to include that in your manufacturing process so that you eliminate any free iron on the surface and create a chromium enriched surface. The copper sulphate test should work fine on this grade without getting false failures. Let us know if you need help.
Lee Kremer
Stellar Solutions, Inc.
McHenry, Illinois
August 11, 2009
Q. To clarify; I'm concerned with the ability to test for free iron on 17-4 PH SS once the steel leaves the mill. Mill material cert indicates that SS microstructure contains less than 1% ferrite. Does this mean that the SS is deemed to be in it's "purist" machine-ready condition when it's shipped to the manufacturer? Would the manufacturer be able to test & identify SS contamination directly from the steel mill, or is it more likely that free iron would produce from the manufacturing process?
My objective is to identify if finished, manufactured product was contaminated via manufacturing processes or if contamination came from the steel mill - in the original raw form. Thank you for your help.
- Traverse City, Michigan
August 18, 2009
A. The less than 1% ferrite in the microstructure is as it says - an inherent part of the microstructure, right through the body of the material. This ferrite is not pure or low-alloy iron, it is a high-chrome constituent that is as corrosion-resistant (in fact slightly more so) as the rest of the microstructure. It is not detected by an iron-contamination test, nor should it be because it is not contamination and does not detract from corrosion resistance.
It is quite unrelated to macrocontamination of the surface by adventitious fragments of ferrous material, such as might come from using steel brushes, or grinding wheels that have previously been used on mild or low-alloy steels. This latter type of contamination is what causes localised corrosion problems if not removed, and is what is detected by the contamination tests.
Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.
August 20, 2009
Q. Knowing that 17-4ph stainless is magnetic, can passivation of this material be performed to allow a copper sulphate test to be negative? (No Rust color)
Kent Danforthaerospace - Oshawa, Ontario, Canada
November 6, 2013
A. That will depend a great deal on how much iron gets smeared on it from tooling during manufacture.
We found that citric worked better on 400 series steel than nitric based ones did and it has no nickel in it. (equal on 300 series)
If that does not work, try a short electropolish process.
Check on one of the supporters of this site. They (she) have an electropolish product that they swear works on 17-4.
- Navarre, Florida
First of two simultaneous responses -- November 8, 2013
A. Kent
Short answer is yes.
See section 14.4.1 of ASTM A967.
- Colorado Springs, Colorado
Second of two simultaneous responses -- November 8, 2013
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