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Crevice Corrosion in a Subsea System — Aspect Before Analysis

Microstructure: Ferritic pearlitic Capture method: Optical Microscope clear all

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BASE METAL SURFACE - Ferritic structure, grain refined.
90
VIEW
ML00177 / Dec.2021
Cr-Mo Seam Welded Tube
M - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Cm - Nital Etched Micrography by OMDf - Base Metal
Metallographic image of a longitudinal section of the clamp (axis in the vertical direction), showing a refined ferritic perlitic structure.
34
VIEW
ML00171 / Feb.2021
Corrosion Fatigue of U Bolt Pipe Clamp
M - Low Carbon SteelP - BoltAp - ShipCd - Corrosion Fatigue
Cm - Nital Etched Micrography by OMDf - Longitudinal Section
The tube microstructure is ferritic-pearlitic, typical of this kind of material. No evidences of microstrutural changes were detected (no overheating, no decarburization).
177
VIEW
ML00163 / Jun.2020
Corrosion Fatigue of a Boiler Waterwall Tube
M - Low Carbon SteelP - Seamless tubeAp - BoilerCd - Corrosion Fatigue
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrography of the pipe base metal, in a longitudinal section, presenting a slight banding and a refined structure.
147
VIEW
ML00153 / Jan.2019
X52 in a Tubular Structure
M - CMn SteelP - Seamless PipeAp - StructureCd - Qualified
Cm - Nital Etched Micrography by OMDf - Base Metal
Micrography of a transverse section of the seamless pipe, presenting a ferritic-pearlitic structure.
84
VIEW
ML00149 / Dec.2018
Vibration Induced Fatigue in a Gas Piping
M - Low Carbon SteelP - Piping spoolAp - FPSOCd - Vibration Induced Fatigue
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrography of the plate in a section, showing a ferritic-pearlitic microstructure in the middle of the thickness.
84
VIEW
ML00143 / Aug.2018
Impact of a .308 Winchester on A36 Plate
M - Low Carbon SteelP - Rolled PlateAp - StructureCd - Pierced
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrographic aspect, as polished, of the cast cylinder section at the fracture position (top of the figure), close to the internal surface (left side). It is possible to see large graphite flakes.
98
VIEW
ML00141 / Jul.2018
Brittle Fracture of a Corroded Gray Cast Iron
M - Gray Cast ironP - CastingAp - EngineCd - Brittle Fracture
Cm - As polished micrographyDf - Close to the Internal Surface
Micrography of the pipe transverse section presenting a granular microstructure.
147
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 - Transverse Section

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ML00177 — Cr-Mo Seam Welded TubeM - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
BASE METAL SURFACE - The micrography (transverse to the tube) presents the ferritic/pearlitic/bainitic structure.
75
VIEW
ML00177 / Dec.2021
Cr-Mo Seam Welded Tube
M - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Cm - Nital Etched Micrography by OMDf - Granular structure
BASE METAL SURFACE - The microstructure of the base metal is ferritic/pearlitic/bainitic.
74
VIEW
ML00177 / Dec.2021
Cr-Mo Seam Welded Tube
M - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Cm - Nital Etched Micrography by OMDf - Grain refined structure
HAZ SURFACE
72
VIEW
ML00177 / Dec.2021
Cr-Mo Seam Welded Tube
M - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Cm - Nital Etched Micrography by OMDf - Last Bead HAZ
HAZ SURFACE
66
VIEW
ML00177 / Dec.2021
Cr-Mo Seam Welded Tube
M - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Cm - Nital Etched Micrography by OMDf - Last Bead HAZ
HAZ SURFACE
55
VIEW
ML00177 / Dec.2021
Cr-Mo Seam Welded Tube
M - CrMo SteelP - Longitudinally Seam WeldedAp - Fired HeaterCd - Not according to spec
Cm - Nital Etched Micrography by OMDf - Bainitic HAZ

+18 more from this case →

ML00171 — Corrosion Fatigue of U Bolt Pipe ClampM - Low Carbon SteelP - BoltAp - ShipCd - Corrosion Fatigue
Metallographic detail of the longitudinal section of the clamp with a ferritic pearlitic structure.
32
VIEW
ML00171 / Feb.2021
Corrosion Fatigue of U Bolt Pipe Clamp
M - Low Carbon SteelP - BoltAp - ShipCd - Corrosion Fatigue
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Metallographic detail of the ferritic perlitic structure.
31
VIEW
ML00171 / Feb.2021
Corrosion Fatigue of U Bolt Pipe Clamp
M - Low Carbon SteelP - BoltAp - ShipCd - Corrosion Fatigue
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Metallographic aspect of a longitudinal section of the clamp, at the surface (left side of the image) showing a region where there are corrosion pits in the carbon steel clamp, due to the lack of protection by the coating, and the propagation of small transgranular cracks from to the surface.
30
VIEW
ML00171 / Feb.2021
Corrosion Fatigue of U Bolt Pipe Clamp
M - Low Carbon SteelP - BoltAp - ShipCd - Corrosion Fatigue
Cm - Micrography by OMDf - Crack
The clamp presented several cracks, parallel, transverse to the axis. The appearance of the cracks in the metallographic section shows that some cracks propagate and growth with a irregular path.
24
VIEW
ML00171 / Feb.2021
Corrosion Fatigue of U Bolt Pipe Clamp
M - Low Carbon SteelP - BoltAp - ShipCd - Corrosion Fatigue
Cm - Nital Etched Micrography by OMDf - Longitudinal Section
Metallographic aspect of the cracks showing that several microcracks join from different pits and growth through the section, in a transgranular morphologyy.
26
VIEW
ML00171 / Feb.2021
Corrosion Fatigue of U Bolt Pipe Clamp
M - Low Carbon SteelP - BoltAp - ShipCd - Corrosion Fatigue
Cm - Nital Etched Micrography by OMDf - Transgranular Cracking

+2 more from this case →

ML00163 — Corrosion Fatigue of a Boiler Waterwall TubeM - Low Carbon SteelP - Seamless tubeAp - BoilerCd - Corrosion Fatigue
The internal side of the tube presented multiple cracks, filled with oxides, blunt-tipped, typical of a corrosion fatigue cracking mechanism.
160
VIEW
ML00163 / Jun.2020
Corrosion Fatigue of a Boiler Waterwall Tube
M - Low Carbon SteelP - Seamless tubeAp - BoilerCd - Corrosion Fatigue
Cm - As polished micrographyDf - Parallel cracks
Micrographic detail of the corrosion cracking from internal side of the tube, in several points at the tube surface.
156
VIEW
ML00163 / Jun.2020
Corrosion Fatigue of a Boiler Waterwall Tube
M - Low Carbon SteelP - Seamless tubeAp - BoilerCd - Corrosion Fatigue
Cm - As polished micrographyDf - Corrosion Cracking
Low magnification micrography of the multiple cracks, parallel, transgranular. No evidences of microstrutural changes (heat evolution or decarburization).
127
VIEW
ML00163 / Jun.2020
Corrosion Fatigue of a Boiler Waterwall Tube
M - Low Carbon SteelP - Seamless tubeAp - BoilerCd - Corrosion Fatigue
Cm - Nital Etched Micrography by OMDf - Transgranular Cracking
Micrography presenting the internal tube surface with several parallel cracks, some still in the beginning (less than 0.1 mm deep).
115
VIEW
ML00163 / Jun.2020
Corrosion Fatigue of a Boiler Waterwall Tube
M - Low Carbon SteelP - Seamless tubeAp - BoilerCd - Corrosion Fatigue
Cm - Nital Etched Micrography by OMDf - Parallel cracks
Micrography of the crack tip, initiated from the internal tube surface. The crack is transgranular, filled with oxides and blunt-tipped.
109
VIEW
ML00163 / Jun.2020
Corrosion Fatigue of a Boiler Waterwall Tube
M - Low Carbon SteelP - Seamless tubeAp - BoilerCd - Corrosion Fatigue
Cm - Nital Etched Micrography by OMDf - Transgranular Cracking

+9 more from this case →

ML00153 — X52 in a Tubular StructureM - CMn SteelP - Seamless PipeAp - StructureCd - Qualified
Micrography of the pipe base metal, in a longitudinal section. The ferritic structure is refined and it is possible to identify a small variation in the ferritic grain size, that is promoting the slight banding effect.
119
VIEW
ML00153 / Jan.2019
X52 in a Tubular Structure
M - CMn SteelP - Seamless PipeAp - StructureCd - Qualified
Cm - Nital Etched Micrography by OMDf - Base Metal
Micrographic detail of the very refined ferritic structure of the base metal, in the longitudinal section, indicating that the material was heat treated, since no banding is not detectable at this magnification.
101
VIEW
ML00153 / Jan.2019
X52 in a Tubular Structure
M - CMn SteelP - Seamless PipeAp - StructureCd - Qualified
Cm - Nital Etched Micrography by OMDf - Grain refined structure
Micrography of the weded joint at the cap pass fusion line. The columnar structure of the weld metal is to the top of the figure; and it is possible to see the coarse grains at the heat affected zone. Both columnar structure and coarse grains are related to the previous austenite grain boundaries. From the fusion line to the base metal (in the bottom of the figure) the grain sizes are refined.
86
VIEW
ML00153 / Jan.2019
X52 in a Tubular Structure
M - CMn SteelP - Seamless PipeAp - StructureCd - Qualified
Cm - Nital Etched Micrography by OMDf - Welded Joint
Micrography presenting the coarse grain heat affected zone of the welded joint, at the cap pass. The microstructure is bainitic.
82
VIEW
ML00153 / Jan.2019
X52 in a Tubular Structure
M - CMn SteelP - Seamless PipeAp - StructureCd - Qualified
Cm - Nital Etched Micrography by OMDf - Heat Affected Zone
Micrographic detail of the bainitic structure of the coarse grain heat affected zone, close to the fusion line (to the top of the figure).
76
VIEW
ML00153 / Jan.2019
X52 in a Tubular Structure
M - CMn SteelP - Seamless PipeAp - StructureCd - Qualified
Cm - Nital Etched Micrography by OMDf - Bainitic HAZ

+5 more from this case →

ML00149 — Vibration Induced Fatigue in a Gas PipingM - Low Carbon SteelP - Piping spoolAp - FPSOCd - Vibration Induced Fatigue
Micrography of a transverse section of the seamless pipe, presenting a ferritic-pearlitic structure.
70
VIEW
ML00149 / Dec.2018
Vibration Induced Fatigue in a Gas Piping
M - Low Carbon SteelP - Piping spoolAp - FPSOCd - Vibration Induced Fatigue
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrography showing the cracking starting point, in the pipe, exactly at the margin of the weld.
292
VIEW
ML00149 / Dec.2018
Vibration Induced Fatigue in a Gas Piping
M - Low Carbon SteelP - Piping spoolAp - FPSOCd - Vibration Induced Fatigue
Cm - Nital Etched Micrography by OMDf - Margin of the Weld Crack
Micrographic detail of the cracking starting point, in the pipe, exactly at the margin of the weld.
33
VIEW
ML00149 / Dec.2018
Vibration Induced Fatigue in a Gas Piping
M - Low Carbon SteelP - Piping spoolAp - FPSOCd - Vibration Induced Fatigue
Cm - Nital Etched Micrography by OMDf - Fatigue Crack
Micrography of a section tranverse to the pipe and to the weld between the 8"pipe and the 2" fitting weldolet. The crack starts exactly at the margin of the weld and propagates in the pipe longitudinal direction, in a straight line, not related to any metallurgical aspect.
30
VIEW
ML00149 / Dec.2018
Vibration Induced Fatigue in a Gas Piping
M - Low Carbon SteelP - Piping spoolAp - FPSOCd - Vibration Induced Fatigue
Cm - Micrography by OMDf - Cracking
Micrographic detail of the fatigue crack propagation in the pipe longitudinal direction, in a straight line, not related to any metallurgical aspect.
29
VIEW
ML00149 / Dec.2018
Vibration Induced Fatigue in a Gas Piping
M - Low Carbon SteelP - Piping spoolAp - FPSOCd - Vibration Induced Fatigue
Cm - Micrography by OMDf - Fatigue Crack

+2 more from this case →

ML00143 — Impact of a .308 Winchester on A36 PlateM - Low Carbon SteelP - Rolled PlateAp - StructureCd - Pierced
Micrography of the plate in a section, showing a ferritic-pearlitic microstructure in the middle of the thickness, in a position where the plate was not affected by the shot.
65
VIEW
ML00143 / Aug.2018
Impact of a .308 Winchester on A36 Plate
M - Low Carbon SteelP - Rolled PlateAp - StructureCd - Pierced
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrographic detail of the plate in a section, showing a ferritic-pearlitic microstructure in the middle of the thickness.
66
VIEW
ML00143 / Aug.2018
Impact of a .308 Winchester on A36 Plate
M - Low Carbon SteelP - Rolled PlateAp - StructureCd - Pierced
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrographic detail of the ferritic-pearlitic microstructure.
53
VIEW
ML00143 / Aug.2018
Impact of a .308 Winchester on A36 Plate
M - Low Carbon SteelP - Rolled PlateAp - StructureCd - Pierced
Cm - Nital Etched Micrography by OMDf - Ferrite and Pearlite
Micrographic detail of the plate section, as polished, close to the surface that suffered the impact. The plate material deformed during the perforation,
31
VIEW
ML00143 / Aug.2018
Impact of a .308 Winchester on A36 Plate
M - Low Carbon SteelP - Rolled PlateAp - StructureCd - Pierced
Cm - As polished micrographyDf - Transverse Section
Micrographic detail of the plate section, as polished, close to the surface that suffered the impact. The copper alloy melted and created a yellow-orange deposit.
25
VIEW
ML00143 / Aug.2018
Impact of a .308 Winchester on A36 Plate
M - Low Carbon SteelP - Rolled PlateAp - StructureCd - Pierced
Cm - As polished micrographyDf - Melted film

+22 more from this case →

ML00141 — Brittle Fracture of a Corroded Gray Cast IronM - Gray Cast ironP - CastingAp - EngineCd - Brittle Fracture
Micrographic aspect, as polished, of the cast cylinder section at the fracture position (top of the figure), in the center of the thickness. It is possible to see a mixture of large graphite flakes and rosette grouping flakes.
80
VIEW
ML00141 / Jul.2018
Brittle Fracture of a Corroded Gray Cast Iron
M - Gray Cast ironP - CastingAp - EngineCd - Brittle Fracture
Cm - As polished micrographyDf - In the Center of the Thickness
Micrographic aspect, as polished, of the cast cylinder section at the fracture position (top of the figure), close to the external surface (left side). It is possible to see smaller graphite flakes, interdendritic .
79
VIEW
ML00141 / Jul.2018
Brittle Fracture of a Corroded Gray Cast Iron
M - Gray Cast ironP - CastingAp - EngineCd - Brittle Fracture
Cm - As polished micrographyDf - Close to the External Surface
Micrography of the longitudinal section of the cylinder, at the internal diameter (left side of the figure), in contact with the treated cooling water, presenting large graphite flakes in a predominatly perlitic matrix.
50
VIEW
ML00141 / Jul.2018
Brittle Fracture of a Corroded Gray Cast Iron
M - Gray Cast ironP - CastingAp - EngineCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Close to the Internal Surface
Micrography of the longitudinal section of the cylinder, at the internal diameter, in contact with the treated cooling water, presenting large graphite flakes in a predominatly perlitic matrix. It is important to mention that the flakes are almost interconnecting themelves.
47
VIEW
ML00141 / Jul.2018
Brittle Fracture of a Corroded Gray Cast Iron
M - Gray Cast ironP - CastingAp - EngineCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Graphite in Flakes
Micrography of the longitudinal section of the cylinder, at the internal diameter, in contact with the treated cooling water, presenting large graphite flakes in a predominatly perlitic matrix. It is important to mention that the flakes are almost interconnecting themelves.
48
VIEW
ML00141 / Jul.2018
Brittle Fracture of a Corroded Gray Cast Iron
M - Gray Cast ironP - CastingAp - EngineCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Predominantly Pearlitic

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ML00140 — Preferential Corrosion of Pipe Seam WeldM - Low Carbon SteelP - Longitudinal Seam Welded PipeAp - ShipCd - Preferential Dissolution
Micrography of the pipe transverse section presenting a predominatly ferritic-perlitic microstructure.
132
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 - Ferrite and Pearlite
Micrographic detail of the predominatly ferritic-perlitic microstructure. Pipe transverse section.
95
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 - Ferrite and Pearlite
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
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

+5 more from this case →