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Dezincification
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Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c0046469
EISBN: 978-1-62708-229-7
... of the tube, extending to a depth of about 0.25 mm (0.010 in.) into the metal, plug-type dezincification extending somewhat deeper into the metal. This supported the conclusion that failure of the tubes was the result of the use of an uninhibited brass that has a high zinc content and therefore is readily...
Abstract
After about 17 years in service, copper alloy C27000 (yellow brass, 65% Cu) innercooler tubes in an air compressor began leaking cooling water, causing failure and requiring replacement. The tubes were 19 mm in diam and had a wall thickness of 1.3 mm (0.050 in.). The cooling water that flowed through the tubes was generally sanitary (chlorinated) well water; however, treated recirculating water was sometimes used. Analysis (visual inspection, 9x and 75x unetched micrographs, and spectrochemical analysis) showed a thick uniform layer of porous, brittle copper on the inner surface of the tube, extending to a depth of about 0.25 mm (0.010 in.) into the metal, plug-type dezincification extending somewhat deeper into the metal. This supported the conclusion that failure of the tubes was the result of the use of an uninhibited brass that has a high zinc content and therefore is readily susceptible to dezincification. Recommendations included replacing the material with copper alloy C68700 (arsenical aluminum brass), which contains 0.02 to 0.06% As and is highly resistant to dezincification. Copper alloy C44300 (inhibited admiralty metal) could be an alternative selection for this application; however, this alloy is not as resistant to impingement attack as copper alloy C68700.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.power.c9001409
EISBN: 978-1-62708-229-7
... Abstract Dezincification is a particular form of corrosive attack which may occur in a variety of environments and to which some brasses are susceptible. It is favored by waters having a high oxygen, carbon dioxide, or chloride content, and is accelerated by elevated temperatures and low water...
Abstract
Dezincification is a particular form of corrosive attack which may occur in a variety of environments and to which some brasses are susceptible. It is favored by waters having a high oxygen, carbon dioxide, or chloride content, and is accelerated by elevated temperatures and low water velocities. In the present study, steam turbine condenser tubes had to be renewed after 25 years of service. The tubes were nominally of 70:30 brass. The appearance of a typically corroded one showed uniform dezincification attack on the bore, extending from one-half to two-thirds through the tube wall thickness.
Book Chapter
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.modes.c9001411
EISBN: 978-1-62708-234-1
... used for bronze welding. Failure resulted from dezincification of the joint material from the internal side of the tube. Also, a selective attack on the beta phase had occurred. It was evident that the loss in mechanical strength arising from the corrosion had resulted in the development of cracking...
Abstract
A welded joint between lengths of 4 in. OD x 13 SWG copper pipe which formed part of a cold-water main failed by cracking over one-third of the circumference. Microscopic examination of the filler metal showed that it had a structure corresponding to a brass of the 60:40 type commonly used for bronze welding. Failure resulted from dezincification of the joint material from the internal side of the tube. Also, a selective attack on the beta phase had occurred. It was evident that the loss in mechanical strength arising from the corrosion had resulted in the development of cracking in service. The filler metal used was not resistant to the conditions to which it was exposed. Copper welding rods as per BS 1077 or a Cu-Ag-P brazing alloy as recommended in BS 699, would have been preferable.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.bldgs.c0091378
EISBN: 978-1-62708-219-8
... deposit analysis, metallurgical examination, and unetched magnified images) supported the conclusion that failure occurred due to porous material typical of plug-type dezincification initiating from the inside surface. Where the dezincification had progressed through the tube wall, the chromium plate had...
Abstract
A 12.7 mm (0.5 in.) diam tube was removed from a potable water supply due to leaks. The tube wall thickness was 0.711 mm (0.028 in.) with a thin layer of chromium plate on the OD surface. The tube had been in service for approximately 33 years. Investigation (visual inspection, EDS deposit analysis, metallurgical examination, and unetched magnified images) supported the conclusion that failure occurred due to porous material typical of plug-type dezincification initiating from the inside surface. Where the dezincification had progressed through the tube wall, the chromium plate had exfoliated from the base material and cracked. Recommendations included replacing the piping with a more corrosion-resistant material such as red brass (UNS C23000), inhibited Admiralty brass (UNS C44300), or arsenical aluminum brass (UNS C68700).
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.bldgs.c9001653
EISBN: 978-1-62708-219-8
..., the color near the key changed from yellow to red-brown. The gate was made from leaded red brass (85-5-5-5) while the spindle was made from silicon brass. It was concluded that the valves failed by dezincification resulting from bimetallic galvanic corrosion. It is common in the valve industry to use...
Abstract
After six years of service, three water shut-off valves on a copper water line in a residential building were found to be inoperative. Macroscopic examination of the valves after disassembly revealed that all three failed at the key that holds the spindle in the gate. In addition, the color near the key changed from yellow to red-brown. The gate was made from leaded red brass (85-5-5-5) while the spindle was made from silicon brass. It was concluded that the valves failed by dezincification resulting from bimetallic galvanic corrosion. It is common in the valve industry to use components made of different alloys in the same valve, but this is not the best approach for all applications.
Series: ASM Failure Analysis Case Histories
Publisher: ASM International
Published: 01 June 2019
DOI: 10.31399/asm.fach.chem.c9001410
EISBN: 978-1-62708-220-4
... of components by the hot stamping process. Microscopic examination indicated failure from dezincification. The fact that the screwed end was not affected indicated that the trouble was not caused by the condensate, which flowed through the elbow, but originated from the water heated in the vessel. The helical...
Abstract
A brass elbow that formed one termination of a steam heating coil failed adjacent to the brazed connection after ten years of service. Chemical analysis showed that the elbow was made from a 60-40 CuZn brass containing 3% lead and 1% tin, a typical alloy used for the manufacture of components by the hot stamping process. Microscopic examination indicated failure from dezincification. The fact that the screwed end was not affected indicated that the trouble was not caused by the condensate, which flowed through the elbow, but originated from the water heated in the vessel. The helical mode of the cracking was probably due to the torsional stresses which would be imposed on the elbow by thermally induced movements of the coil in service.
Series: ASM Failure Analysis Case Histories
Volume: 2
Publisher: ASM International
Published: 01 December 1993
DOI: 10.31399/asm.fach.v02.c9001373
EISBN: 978-1-62708-215-0
... of the valves failed by dezincification. The porous copper matrix could not sustain the clamping loads imposed by tightening the pressure relief fitting. The second valve failed by shear overload of the pressure relief fitting. Overload was facilitated by a reduction of cross-sectional area caused...
Abstract
Two new chrome-plated CDA 377 brass valves intended for inert gas service failed on initial installation. After a pickling operation to clean the metal, the outer surfaces of the valves had been flashed with copper and then plated with nickel and chromium for aesthetic purposes. One of the valves failed by dezincification. The porous copper matrix could not sustain the clamping loads imposed by tightening the pressure relief fitting. The second valve failed by shear overload of the pressure relief fitting. Overload was facilitated by a reduction of cross-sectional area caused by intergranular attack and slight dezincification of the inner bore surface of the fitting. Dezincification and intergranular attack were attributed to excessive exposure to nonoxidizing acids in the pickling bath.
Image
in Dezincification of Brass Tubes in a Steam Turbine Condenser
> ASM Failure Analysis Case Histories: Power Generating Equipment
Published: 01 June 2019
Fig. 1 Condenser tube affected by dezincification. (×5)
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Image
in Dezincification of Brass Tubes in a Steam Turbine Condenser
> ASM Failure Analysis Case Histories: Power Generating Equipment
Published: 01 June 2019
Fig. 2 Dezincification (unetched). (×50)
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Image
in Dezincification of Brass Tubes in a Steam Turbine Condenser
> ASM Failure Analysis Case Histories: Power Generating Equipment
Published: 01 June 2019
Fig. 3 Dezincification (etched). (×100)
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Image
in Dezincification of a Brass Elbow in a Steam Heating Coil
> ASM Failure Analysis Case Histories: Chemical Processing Equipment
Published: 01 June 2019
Fig. 1 Elbow affected by dezincification. × 5
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Image
in Dezincification of Silicon Brass in Contact with Leaded Red Brass
> ASM Failure Analysis Case Histories: Buildings, Bridges, and Infrastructure
Published: 01 June 2019
Fig. 1 Dezincification of silicon brass spindle (unetched, 5.5×).
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Image
in Microstructural Analysis of the Brass Seat of a Valve from the 1907 Steam Tug ‘Hercules’
> ASM Failure Analysis Case Histories: Mechanical and Machine Components
Published: 01 June 2019
Fig. 12 Zn-depleted region in the nut showing selective dezincification of the β phase.
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in Dezincification of a Chrome-Plated Cylinder Gas Valve
> Handbook of Case Histories in Failure Analysis
Published: 01 December 1993
Fig. 4 Micrograph showing the depth of dezincification in the pressure relief valve threads of the first valve. 31.5×
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Image
in Dezincification of a Chrome-Plated Cylinder Gas Valve
> Handbook of Case Histories in Failure Analysis
Published: 01 December 1993
Fig. 7 Minute dezincification under the plating of the second valve. Etched with NH 4 OH/H 2 O 2 . 630×
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Image
in Dezincification of a Chrome-Plated Cylinder Gas Valve
> Handbook of Case Histories in Failure Analysis
Published: 01 December 1993
Fig. 8 Intergranular cracking and dezincification in the inner bore surface of the pressure relief part of the second valve. Unetched. 315×
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Image
in Dezincification of a Chrome-Plated Cylinder Gas Valve
> Handbook of Case Histories in Failure Analysis
Published: 01 December 1993
Fig. 9 Dezincification on the inner surface in the neck of the first valve. Etched with NH 4 OH/H 2 O 2 . 63×
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Image
in Dezincification of a Chrome-Plated Cylinder Gas Valve
> Handbook of Case Histories in Failure Analysis
Published: 01 December 1993
Fig. 10 Micrograph showing only traces of dezincification on the surface of the second valve. 630×
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Image
in Dezincification of a Chromium-Plated Copper Alloy Tube
> ASM Failure Analysis Case Histories: Buildings, Bridges, and Infrastructure
Published: 01 June 2019
Fig. 1 Views of a through-wall perforation of a chromium-plated α brass (70Cu-30Zn) tube removed from a potable water system due to dezincification. (a) Macroview of tube. (b) Inside diameter surface of the tube shown in (a), depicting localized green deposits at the areas of dezincification
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Series: ASM Failure Analysis Case Histories
Volume: 1
Publisher: ASM International
Published: 01 December 1992
DOI: 10.31399/asm.fach.v01.c9001045
EISBN: 978-1-62708-214-3
... and scanning electron microscopy were used to examine samples from the tubes. An energy-dispersive electron microprobe analysis was carried out to evaluate the zinc distribution. Results showed that the failure was due to dezincification. Replacement of the tubes with new tubes fabricated from...
Abstract
A failure analysis was conducted on brass alloy 270 heat exchanger tubes that were pulled from a unit used to cool oil for the speed regulators and thrust bearings of a hydroelectric power plant. The tubes began to leak after approximately 5.5 years of service. Macrophotography and scanning electron microscopy were used to examine samples from the tubes. An energy-dispersive electron microprobe analysis was carried out to evaluate the zinc distribution. Results showed that the failure was due to dezincification. Replacement of the tubes with new tubes fabricated from a dezincification-resistant alloy was recommended.