scholarly journals In Situ Monitoring of Corrosion under Insulation Using Electrochemical and Mass Loss Measurements

2022 ◽  
Vol 2022 ◽  
pp. 1-12
Author(s):  
Mingzhang Yang ◽  
Jing Liu
Keyword(s):  
Thermal Cycling ◽  
Mass Loss ◽  
Thermal Insulation ◽  
Polarization Resistance ◽  
Operating Conditions ◽  
In Situ Monitoring ◽  
Pipe Surface ◽  
Eis Measurements ◽  
Corrosion Under Insulation

Corrosion under insulation (CUI) refers to the external corrosion of piping and vessels when they are encapsulated in thermal insulation. To date, very limited information (especially electrochemical data) is available for these “difficult-to-test” CUI conditions. This study was aimed at developing a novel electrochemical sensing method for in situ CUI monitoring and analysis. Pt-coated Ti wires were used to assemble a three-electrode electrochemical cell over a pipe surface covered by thermal insulation. The CUI behavior of X70 carbon steel (CS) and 304 stainless steel (SS) under various operating conditions was investigated using mass loss, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) measurements. It was found that both the consecutive wet and dry cycles and cyclic temperatures accelerated the progression of CUI. LPR and EIS measurements revealed that the accelerated CUI by thermal cycling was due to the reduced polarization resistance and deteriorated corrosion film. Enhanced pitting corrosion was observed on all tested samples after thermal cycling conditions, especially for CS samples. The proposed electrochemical technique demonstrated the ability to obtain comparable corrosion rates to conventional mass loss data. In addition to its potential for in situ CUI monitoring, this design could be further applied to rank alloys, coatings, and inhibitors under more complex exposure conditions.

scholarly journals Thermal Assessment and In-Situ Monitoring of Insulated Gate Bipolar Transistors in Power Electronic Modules

2019 ◽  
Author(s):  
Erick Gutierrez ◽  
Kevin Lin ◽  
Douglas DeVoto ◽  
Patrick McCluskey
Keyword(s):  
Thermal Cycling ◽  
Failure Modes ◽  
Rapid Determination ◽  
Degradation Process ◽  
In Situ Monitoring ◽  
Power Module ◽  
Insulated Gate Bipolar Transistor ◽  
Die Attach ◽  
Power Modules

Abstract Insulated gate bipolar transistor (IGBT) power modules are devices commonly used for high-power applications. Operation and environmental stresses can cause these power modules to progressively degrade over time, potentially leading to catastrophic failure of the device. This degradation process may cause some early performance symptoms related to the state of health of the power module, making it possible to detect reliability degradation of the IGBT module. Testing can be used to accelerate this process, permitting a rapid determination of whether specific declines in device reliability can be characterized. In this study, thermal cycling was conducted on multiple power modules simultaneously in order to assess the effect of thermal cycling on the degradation of the power module. In-situ monitoring of temperature was performed from inside each power module using high temperature thermocouples. Device imaging and characterization were performed along with temperature data analysis, to assess failure modes and mechanisms within the power modules. While the experiment aimed to assess the potential damage effects of thermal cycling on the die attach, results indicated that wire bond degradation was the life-limiting failure mechanism.

Investigation of Temperature Limitations During Rapid Thermal Cycling of a Micro-Tubular Flame-Assisted Fuel Cell

2020 ◽  
Author(s):  
Ryan J. Milcarek ◽  
Rhushikesh Ghotkar ◽  
Jeongmin Ahn
Keyword(s):  
Fuel Cell ◽  
Thermal Cycling ◽  
Power Density ◽  
Thermal Insulation ◽  
Current Collector ◽  
Operating Conditions ◽  
Slow Heating ◽  
Maximum Temperature ◽  
Sofc Cathode ◽  
Rapid Thermal Cycling

Abstract Despite many efforts and improvements over the last few decades, two of the major challenges facing Solid Oxide Fuel Cells (SOFCs) are slow heating rates to operating conditions (typically < 5 °C.min−1) and a limited ability to thermal cycle (< 200 cycles). Recently a novel hybridized setup that combines a fuel-rich combustion reformer with a SOFC was developed and utilized to investigate rapid heating, cooling and thermal cycling of a micro-Tubular SOFC. The setup places the SOFC directly in the flame and exhaust of the high temperature combustion of methane, which allows for extremely rapid temperature rise in the SOFC. A SOFC with a (La0.8Sr0.2)0.95MnO3-x cathode was tested in the setup, but limitations on air preheating for the cathode resulted in low SOFC cathode temperatures (∼500°C) and low power density. Thermal insulation improved pre-heating of the air delivered to the cathode, increased the SOFC cathode temperature and, when a (La0.60Sr0.40)0.95Co0.20Fe0.80O3-x cathode was applied to the SOFC, resulted in improved power density. After adjusting the thermal insulation, the air temperature near the cathode exceeded ∼750°C during testing. Over 3,000 thermal cycles were conducted at a heating rate exceeding 900°C.min−1 and a cooling rate that exceeded 300°C.min−1. The open circuit voltage was analyzed over the 150 h test and a low degradation rate of ∼0.0008V per 100 cycles per fuel cell was observed. Unlike the previous test, which was conducted at lower temperatures, significant degradation of the current collector was observed during this test. Electrochemical impedance spectroscopy shows that degradation in the SOFC was due to increases in ohmic losses, activation losses at the cathode and increased concentration losses. The setup demonstrates that rapid thermal cycling of micro-Tubular SOFCs can be achieved, but there are limitations on the maximum temperature that can be sustained depending on the current collector.

scholarly journals In situ monitoring of corrosion mechanisms and phosphate inhibitor surface deposition during corrosion of zinc–magnesium–aluminium (ZMA) alloys using novel time-lapse microscopy

2015 ◽  
Vol 180 ◽  
pp. 361-379 ◽  
Author(s):  
James Sullivan ◽  
Nathan Cooze ◽  
Callum Gallagher ◽  
Tom Lewis ◽  
Tomas Prosek ◽  
...  
Keyword(s):  
Image Analysis ◽  
Mass Loss ◽  
Alloy System ◽  
Time Lapse ◽  
Open Circuit ◽  
In Situ Monitoring ◽  
Corrosion Mechanism ◽  
Saturation Effects ◽  
Corrosion Mechanisms

In situtime-lapse optical microscopy was used to examine the microstructural corrosion mechanisms in three zinc–magnesium–aluminium (ZMA) alloy coated steels immersed in 1% NaCl pH 7. Preferential corrosion of MgZn2lamellae within the eutectic phases was observed in all the ZMA alloys followed by subsequent dissolution of Zn rich phases. The total extent and rate of corrosion, measured using time-lapse image analysis and scanning vibrating electrode technique (SVET) estimated mass loss, decreased as Mg and Al alloying additions were increased up to a level of 3 wt% Mg and 3.7 wt% Al. This was probably due to the increased presence of MgO and Al2O3at the alloy surface retarding the kinetics of cathodic oxygen reduction. The addition of 1 × 10−2mol dm−3Na3PO4to 1% NaCl pH 7 had a dramatic influence on the corrosion mechanism for a ZMA with passivation of anodic sites through phosphate precipitation observed using time-lapse image analysis. Intriguing rapid precipitation of filamentous phosphate was also observed and it is postulated that these filaments nucleate and grow due to super saturation effects. Polarisation experiments showed that the addition of 1 × 10−2mol dm−3Na3PO4to the 1% NaCl electrolyte promoted an anodic shift of 50 mV in open circuit potential for the ZMA alloy with a reduction in anodic current of 2.5 orders of magnitude suggesting that it was acting primarily as an anodic inhibitor supporting the inferences from the time-lapse investigations. These phosphate additions resulted in a 98% reduction in estimated mass loss as measured by SVET demonstrating the effectiveness of phosphate inhibitors for this alloy system.

Cathodoluminescence of Catalyst Crystallites

1982 ◽  
Vol 40 ◽  
pp. 664-665
Author(s):  
E.D. Boyes ◽  
P.L. Gai ◽  
D.B. Darby ◽  
C. Warwick
Keyword(s):  
Defect Density ◽  
Chemical Properties ◽  
Operating Conditions ◽  
Semiconductor Materials ◽  
Environmental Cell ◽  
High Resolution Structure ◽  
Commercially Important ◽  
Crystallographic Defects ◽  
Resolution Structure

The extended crystallographic defects introduced into some oxide catalysts under operating conditions may be a consequence and accommodation of the changes produced by the catalytic activity, rather than always being the origin of the reactivity. Operation without such defects has been established for the commercially important tellurium molybdate system. in addition it is clear that the point defect density and the electronic structure can both have a significant influence on the chemical properties and hence on the effectiveness (activity and selectivity) of the material as a catalyst. SEM/probe techniques more commonly applied to semiconductor materials, have been investigated to supplement the information obtained from in-situ environmental cell HVEM, ultra-high resolution structure imaging and more conventional AEM and EPMA chemical microanalysis.

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