Effects of Cr Content and Environmental Factors on FAC Rate of Carbon Steels

Combined effects of Cr content and environmental factors, pH and dissolved oxygen concentration, on removal rate of carbon steels due to flow accelerated corrosion have been examined by experiments. The effects of environmental factors on FAC rate have been attempted to interpret based on oxide solubility, which has been precisely evaluated by separate experiments and numerical estimations. pH dependency of the FAC rate has been found to be directly related to solubility of magnetite. Cr content holds a strong impact on the FAC rate regardless of pH values from 6.84 to 10.4. Addition of 1% Cr to a carbon steel reduces the FAC rate by one order of magnitude under the environmental conditions, where magnetite forms. Addition of oxygen up to 1200ppb changes the oxide from magnetite to hematite, resulting in significant improvement in corrosion resistance. Oxide film characteristics, e.g. compositional distributions and types of oxide compound, have been also examined and their correlation to the FAC rate has been discussed.

Effect of Material Factors on FAC Rate and Characteristics of Oxide Layer

ASME 2010 Pressure Vessels and Piping Conference: Volume 6, Parts A and B ◽

10.1115/pvp2010-25584 ◽

2010 ◽

Author(s):

Yutaka Watanabe ◽

Hiroshi Abe ◽

Takamichi Miyazaki

Keyword(s):

Oxide Layer ◽

Defect Density ◽

Carbon Steels ◽

Metal Interface ◽

Accelerated Corrosion ◽

Cr Content ◽

Transmission Electron ◽

Scale Characteristics ◽

Cr Concentration ◽

Combined effects of Cr content and pH on corrosion rate of carbon steels due to flow accelerated corrosion have been examined by experiments and their relation to oxide scale characteristics based on detailed oxide layer characterizations using transmission electron microscope with X-ray analyzer have been discussed. Effect of Cr content on FAC mitigation decrease continuously as pH is increased from neutral to 10.4 and effect of pH on that increase significantly from pH 9.1 to 9.4. Obvious Cr enrichment has been observed in the oxide layer of 1.01 wt% Cr content steel regardless pH condition. Cr concentration is highest at top surface of oxide layer, and that decrease from surface to oxide / metal interface gradually. It has been suggested that Cr enrichment stabilize oxide layer (decrease solubility and defect density of oxide layer), as a result, FAC suppressed.

The Minerals, Metals & Materials Series - Proceedings of the 18th International Conference on Environmental Degradation of Materials in Nuclear Power Systems – Water Reactors ◽

Investigation of Flow Accelerated Corrosion Models to Predict the Corrosion Behavior of Coated Carbon Steels in Secondary Piping Systems

10.1007/978-3-030-04639-2_67 ◽

2017 ◽

pp. 1067-1076

Author(s):

Seunghyun Kim ◽

Ji Hyun Kim

Keyword(s):

Corrosion Behavior ◽

Carbon Steels ◽

Accelerated Corrosion ◽

Piping Systems ◽

Coated Carbon

Development of Statistical Modeling Methodology for Flow Accelerated Corrosion: Effect of Flow Rate, Water Temperature, pH, and Cr Content

Transactions of the Korean Society of Pressure Vessels and Piping ◽

10.20466/kpvp.2016.12.2.040 ◽

2016 ◽

Vol 12 (2) ◽

pp. 40-49

Author(s):

Gyeong-Geun Lee ◽

Eun Hee Lee ◽

Sung-Woo Kim ◽

Dong-Jin Kim

Keyword(s):

Water Temperature ◽

Statistical Modeling ◽

Flow Rate ◽

Accelerated Corrosion ◽

Cr Content ◽

Corrosion Effect ◽

Modeling Methodology ◽

A233 Relationship between thinning rate of carbon steels due to flow-accelerated corrosion and characteristics of oxide films formed

The Proceedings of the National Symposium on Power and Energy Systems ◽

10.1299/jsmepes.2015.20.205 ◽

2015 ◽

Vol 2015.20 (0) ◽

pp. 205-208

Author(s):

Takuma YANO ◽

Hiroshi ABE ◽

TAKAMICHI Miyazaki ◽

Yutaka WATANABE ◽

Kazutoshi FUJIWARA ◽

...

Keyword(s):

Oxide Films ◽

Carbon Steels ◽

Accelerated Corrosion ◽

Thinning Rate

Flow Accelerated Corrosion of Carbon Steel with Droplet Impingement Using a Modified Rotating Cylinder Electrode Experiment

CORROSION ◽

10.5006/3345 ◽

2020 ◽

Vol 76 (2) ◽

pp. 202-209 ◽

Cited By ~ 1

Author(s):

Amna Esayah ◽

Madison Kelley ◽

Andrew Howell ◽

Stephen J. Shulder ◽

Brajendra Mishra ◽

...

Keyword(s):

Electrochemical Impedance ◽

Rotating Cylinder ◽

Liquid Films ◽

Electrode System ◽

Carbon Steels ◽

Protective Oxide ◽

Droplet Impingement ◽

Accelerated Corrosion ◽

Rotating Cylinder Electrode ◽

In power plant cooling systems, water droplets and condensate films form due to heat transfer through cooling tube walls. Condensate films are known to cause flow accelerated corrosion on carbon steels used in air-cooled condensers. Corrosion is further accelerated by droplets suspended in the accelerating steam that impinge on walls, T-joints, or valves, further damaging protective oxide layers on pipe walls. Droplet impingement and flow accelerated corrosion were studied using a modified rotating cylinder electrode system coupled with electrochemical impedance spectroscopy. Surface liquid films caused by droplet impingement were found to correlate directly with flow accelerated corrosion caused by condensate films. In the absence of a stable liquid film, droplet impingement increased corrosion rates and resulted in pit formation. Select corrosion inhibitors were found to be ineffective under flow accelerated corrosion or droplet impingement.

Predicting and Preventing Flow Accelerated Corrosion in Nuclear Power Plant

International Journal of Nuclear Energy ◽

10.1155/2014/423295 ◽

2014 ◽

Vol 2014 ◽

pp. 1-23 ◽

Cited By ~ 7

Author(s):

Bryan Poulson

Keyword(s):

Mass Transfer ◽

Nuclear Power ◽

Mass Transfer Rate ◽

Environmental Parameters ◽

Theoretical Models ◽

Carbon Steels ◽

Accelerated Corrosion ◽

Material Factor ◽

Over 40 Years

Flow accelerated corrosion (FAC) of carbon steels in water has been a concern in nuclear power production for over 40 years. Many theoretical models or empirical approaches have been developed to predict the possible occurrence, position, and rate of FAC. There are a number of parameters, which need to be incorporated into any model. Firstly there is a measure defining the hydrodynamic severity of the flow; this is usually the mass transfer rate. The development of roughness due to FAC and its effect on mass transfer need to be considered. Then most critically there is the derived or assumed functional relationship between the chosen hydrodynamic parameter and the rate of FAC. Environmental parameters that are required, at the relevant temperature and pH, are the solubility of magnetite and the diffusion coefficient of the relevant iron species. The chromium content of the steel is the most important material factor.

The Minerals, Metals & Materials Series - Proceedings of the 18th International Conference on Environmental Degradation of Materials in Nuclear Power Systems – Water Reactors ◽

Investigation of Flow Accelerated Corrosion Models to Predict the Corrosion Behavior of Coated Carbon Steels in Secondary Piping Systems

10.1007/978-3-319-67244-1_67 ◽

2017 ◽

pp. 1067-1076

Author(s):

Seunghyun Kim ◽

Ji Hyun Kim

Keyword(s):

Corrosion Behavior ◽

Carbon Steels ◽

Accelerated Corrosion ◽

Piping Systems ◽

Coated Carbon

Influence of bend geometry on flow accelerated corrosion under neutral pH conditions

Engineering Failure Analysis ◽

10.1016/j.engfailanal.2020.105127 ◽

2021 ◽

Vol 122 ◽

pp. 105127

Author(s):

P. Madasamy ◽

M. Mukunthan ◽

P. Chandramohan ◽

T.V. Krishna Mohan ◽

Andrews Sylvanus ◽

...

Keyword(s):

Accelerated Corrosion ◽

Neutral Ph ◽

Ph Conditions ◽

Flow-accelerated corrosion assessment for SA106 and SA335 pipes with elbows and welds

Nuclear Engineering and Technology ◽

10.1016/j.net.2021.03.026 ◽

2021 ◽

Author(s):

Dong-Jin Kim ◽

Sung-Woo Kim ◽

Jong Yeon Lee ◽

Kyung Mo Kim ◽

Se Beom Oh ◽

...

Keyword(s):

Accelerated Corrosion ◽

Corrosion Assessment ◽

Volume 2: Structural Integrity; Safety and Security; Advanced Applications of Nuclear Technology; Balance of Plant for Nuclear Applications ◽

Analytical Investigation of Deaerator Steam Inlet Nozzle Corrosion Allowance in a CANDU Station

10.1115/icone17-75617 ◽

2009 ◽

Author(s):

Ali Keshavarz ◽

Andrew K. Ali ◽

Randy K. Lall

Keyword(s):

Finite Element ◽

Carbon Steel ◽

Stress Analysis ◽

Analytical Investigation ◽

Percentage Error ◽

Metal Loss ◽

Fe Model ◽

Accelerated Corrosion ◽

Materials Properties ◽

Flow-accelerated corrosion (FAC) is a phenomenon that results in metal loss from piping, vessels and equipment made of carbon steel. This metal loss can lead to stress to occur at the steam inlet nozzle side, where it is located at the side of the deaerator. This paper presents a method to find the thickness critical of the steam inlet nozzle. A Finite Element (FE) model of the pressure vessel head was created to perform a stress analysis using NX Nastran 5.0. By applying materials properties, loads and constraints to the model, the results obtained are required to satisfy the following criterion: vonMises≥SySy=YieldStrength The results obtained from the stress analysis were analyzed to obtain a corrosion allowance and it was compared to the recommended value from a normal deaerator design, which is roughly 0.25 inches. From the FE model, and by continuously reducing the thickness of the nozzle, it was determined that the corrosion allowance is 0.229 inches, and that the percentage error was 8.4%.