Oxalic Acid Electrolytic Etch

1 case · 5 images

Crevice Corrosion in a Subsea System — Aspect Before Analysis

Microstructure: Intragranular Intergranular Precipitates Detail focus: Austenitic with Secondary Precipitation clear all

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SAMPLE 1 AT THE FRACTURE - Micrography at the position where the thickness is reduced to zero. Side A to the bottom. The microstructure is austenite with intergranular and transgranular precipitation. The position of the zero thickness presents aspect of an intergranular fracture, and in side A there are several intergranular cracks from the surface.
83
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Austenitic with Secondary Precipitation

More from these cases

ML00160 — High Temperature Degradation of 310SSM - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
SAMPLE 1 AT 1 mm THICKNESS - Micrography in the center of the thickness. The microstructure is austenitic with secondary precipitation, intergranular and intragranular.
76
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Austenitic with Secondary Precipitation
SAMPLE 1 AT 1 mm THICKNESS - Micrographic detail of the austenite with secondary precipitation. This oxalic acid electrolytic etch is revealing the integranular and transgranular (or intragranular) precipitation. In the grain boundaries it is possible to see: 1) a continuous network of carbide precipitation and 2) isolated islands of sigma phase. In the middle of the grains there are rounded and neddles like carbides.
72
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Austenitic with Secondary Precipitation
SAMPLE 1 AT 1 mm THICKNESS, SIDE A - Micrographic detail of the austenite with secondary precipitation, close to the surface exposed to the process side. This oxalic acid electrolytic etch is revealing the sigma phase at austenite grain boundaries that is probably intensifying the intergranular oxidation, creating cracks and grain detachemnt leading to quick thinning.
40
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Austenitic with Secondary Precipitation
SAMPLE 1 AT 1 mm THICKNESS, SIDE B - Micrographic detail of the austenite with secondary precipitation, close to the surface exposed to the furnace environment. Although the microstructure is similar all througth the thickness, there are no oxide penetrations into the grain boundaries, even close to the fracture, indicating that the environment is less aggressive.
26
VIEW
ML00160 / Apr.2020
High Temperature Degradation of 310SS
M - Austenitic Stainless SteelP - Rectangular TubeAp - Chemical IndustryCd - Scaling
Cm - Oxalic Acid Electrolytic EtchDf - Austenitic with Secondary Precipitation