Comparative Assessment of Metallographic Etching Methods for Duplex Stainless-Steel Welds

Six etchants for metallographic preparation of AISI 2205 duplex stainless-steel welded joints were investigated. Three chemical reagents (Kalling No. 2, Vilella, and Modified Vander Arend) and three electrolytic etchants (40% KOH, 10% oxalic acid, and saturated ammonium persulfate) were evaluated. Kalling No. 2 and modified Vilella produced clear ferrite ( δ )–austenite ( γ ) contrast in the base and weld metals but were less effective in the heat-affected zone (HAZ). The Modified Vander Arend reagent, although slower, enabled the visualization of all regions while preserving secondary phases and inclusions. Among the electrolytic etchants, oxalic acid provided strong contrast but induced severe localized corrosion, whereas KOH resulted in moderate anodic dissolution and superior preservation of microstructural features. Ammonium persulfate produced uniform contrast but partially dissolved ferrite ( δ ) in the vicinity of precipitates. Overall, the results show that the selection of the most appropriate etchant depends on the balance between microstructural delineation and surface preservation. This balance must be considered according to the microstructural features of interest.