Ferrite Content
This is a photo of Duplex Stainless Steel in the etched condition. Ferrite content is determined by taking a photo of the structure and laying a gid over the picture. The grids intersection points which fall on the white structure is counted, and divided by the total points of the grid. This gives you very accurate percentages of ferrite content. The Ferrite is the colored areas, Austenite is the white color which was un-affected by the etching process. This is governed by ASTM-A-923.