Optical Microscope

2 cases · 17 images

Crevice Corrosion in a Subsea System — Aspect Before Analysis

Application: Ship Condition: Preferential Dissolution Detail focus: Damage clear all

Optical Microscope — sub-branches

As polished micrography 6FeCl3+HCl+Ethanol Etched Micro 4Nital Etched Micrography by OM 7

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Micrography of the pipe in the leakage area, showing the preferential corrosion in the center of the autogenous weld and oxides inside the crevice, that appearas as a cracking but that is only a localized anodic process.
66
VIEW
ML00140 / May.2019
Preferential Corrosion of Pipe Seam Weld
M - Low Carbon SteelP - Longitudinal Seam Welded PipeAp - ShipCd - Preferential Dissolution
Cm - Nital Etched Micrography by OMDf - Localized Corrosion
Micrography of the transverse section of the platesheet at the interface between the corroded and the non-corroded regions. The micrography is in the as polished condition.
140
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - As polished micrographyDf - Preferential Dissolution

More from these cases

ML00140 — Preferential Corrosion of Pipe Seam WeldM - Low Carbon SteelP - Longitudinal Seam Welded PipeAp - ShipCd - Preferential Dissolution
Micrographic detail of the autogenous seam weld. The localized dissolution occurrs exactly at the weld metal that presents a bainitic structure of average hardness about 230HV, compared to the heat affected zone presenting average of 202 HV and the base metal presenting average of 180HV.
57
VIEW
ML00140 / May.2019
Preferential Corrosion of Pipe Seam Weld
M - Low Carbon SteelP - Longitudinal Seam Welded PipeAp - ShipCd - Preferential Dissolution
Cm - Nital Etched Micrography by OMDf - Localized Corrosion
Micrographic detail presenting the slighltly decarburized ferritic structure, with inclusions, in the center of the weld, surrounded by a bainitic structure and the preferential corrosion in the weld.
51
VIEW
ML00140 / May.2019
Preferential Corrosion of Pipe Seam Weld
M - Low Carbon SteelP - Longitudinal Seam Welded PipeAp - ShipCd - Preferential Dissolution
Cm - Nital Etched Micrography by OMDf - Localized Corrosion
Micrography of the pipe in the leakage area, at the internal pipe surface, showing the preferential corrosion in the center of the autogenous weld and oxides inside the crevice. The morphology of the corrosion is similar to a cracking but the analysis show that it is a localized anodic process.
45
VIEW
ML00140 / May.2019
Preferential Corrosion of Pipe Seam Weld
M - Low Carbon SteelP - Longitudinal Seam Welded PipeAp - ShipCd - Preferential Dissolution
Cm - Nital Etched Micrography by OMDf - Preferential Dissolution
Micrography of the pipe at the leakage position showing an oxide layer inside the crevice. The corrosion occurred exactly at the weld metal and the region at the margin of the damage shows the heat affected zone of the autogenous weld, with a refined grain size.
41
VIEW
ML00140 / May.2019
Preferential Corrosion of Pipe Seam Weld
M - Low Carbon SteelP - Longitudinal Seam Welded PipeAp - ShipCd - Preferential Dissolution
Cm - Nital Etched Micrography by OMDf - Preferential Dissolution
Micrography of the internal pipe surface at the leakage position showing an oxide layer inside the crevice. The corrosion occurred exactly at the weld metal and the region at the margin of the damage shows the heat affected zone of the autogenous weld, with a refined grain size.
40
VIEW
ML00140 / May.2019
Preferential Corrosion of Pipe Seam Weld
M - Low Carbon SteelP - Longitudinal Seam Welded PipeAp - ShipCd - Preferential Dissolution
Cm - Nital Etched Micrography by OMDf - Preferential Dissolution

+1 more from this case →

ML00125 — Dezincification of a Cooler TubesheetM - BrassP - PlateAp - ShipCd - Preferential Dissolution
Micrography of the transverse section of the platesheet showing that part of the material (right side in the top of the figure) was lost (corroded).
129
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - As polished micrographyDf - Preferential Dissolution
Micrographic detail of the dezincification effect, where the beta phase is preferentially corroded, leaving a cooper rich phase (red) that is porous and easily cracks.
121
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - As polished micrographyDf - Dezincification
Micrographic detail of the dezincification effect, where the beta phase is preferentially corroded, leaving a cooper rich phase (red) that is porous and easily cracks.
130
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - As polished micrographyDf - Cracks
Micrography showing detachment of material at the surface of the platesheet. The cracks are associated to the dezincification effect, where the beta phase was preferentially corroded and became a weak porous layer.
113
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - As polished micrographyDf - Crack
Micrography presenting the interface between the layer where the dezincification occurred (top of the figure) and the region where the material was not yet corroded (bottom of the figure).
86
VIEW
ML00125 / Mar.2018
Dezincification of a Cooler Tubesheet
M - BrassP - PlateAp - ShipCd - Preferential Dissolution
Cm - As polished micrographyDf - Dezincification

+4 more from this case →