Ferroxyl test

FERROXYL TEST

Ferroxyl Test (available from Trawialnia.eu) is performed to determine whether austenitic stainless steel requires pickling or to assess whether the pickling process has been carried out properly. The test complies with ASTM A380 and ASTM A967 standards.

If the surface structure of austenitic stainless steel has not been uniformly renewed and metallic iron (known as free iron) is detected, the properties of the stainless steel will be compromised. The presence of free iron on the surface damages the thin chromium oxide layer, resulting in a localized decrease in corrosion resistance.
If the free iron is not removed, serious pitting corrosion can occur.

The test is based on the reaction of potassium ferricyanide with iron under strongly acidic conditions. Free iron dissolves in the strongly acidic medium, transitioning into ferrous ions that react to form a compound known as Prussian blue. If a blue color appears during the test, it indicates that the surface of the stainless steel has not been properly prepared — i.e. the pickling process was not performed correctly. However, if no blue color develops (the filter paper surface remains clean), it means that the pickling process was satisfactory.

The kit contains pre-prepared reagents that can be easily mixed together. Using a pipette, moisten the filter paper with the test solution and place it onto the surface being tested. Wait for approximately 1 minute. If a blue color appears (even small blue spots), the surface was not properly pickled, and free iron is present. If no blue color develops, the pickling was successful. Finally, after removing the paper, thoroughly rinse the tested area with demineralized water to wash off any remaining test solution.