Ferrite inspection or ferrite testing is a non-destructive testing method which is carried out mainly on austenitic stainless steel and Duplex material. The ferrillium count is measured by the means of a small probe utilising the magnetic induction test method. This is where the ferrite content is obtained from the magnetic permeability.
To perform ferrite testing properly, both a minimum material thickness and a minimum specimen size are required. Test results are interpreted in accordance with current specifications and/or customer requirements and are displayed as a percentage.