Corrosion Simulation Newsletter
Determination of anode resistance to ground is typically an integral part of cathodic protection system designs. However, complications in this process arise when anodes are located close together as mutual interference effects become important, often resulting in significant reduction in effective output. Such considerations can apply for anodes on structures, on sleds and between sleds (if multiple sleds are required such as can be needed, for example, with retrofit installations).
|Contours of current density on the anode surfaces (blue=low, red=high) Chart shows Dwight data (green)for interference ratio of a sled with 3 anodes, with extrapolation to smaller anode spacings. At 1.64 ft (0.5m) spacing, Dwight exaggerates the sled current by 30%|
If you have concerns about the reduction in effectiveness resulting from the need to locate anodes in close proximity to one another, and want to understand how the impact can be readily determined, please contact us.
BEASY paper presented at NACE Corrosion 2019
How to Improve Accuracy of Anode Output Estimated From Field Gradient Measurements
By John Baynham and Tim Froome
At Corrosion 2019, BEASY presented a paper addressing a number of factors that can impact the interpretation of measurements taken during survey with probes incorporating two reference electrodes.
Typical practice is to convert the potential difference between the two electrodes into an estimated anode output. There are, however, risks that those values may be inaccurate if appropriate consideration is not taken of factors such as:
- The stab being taken at a location away from the middle of the anode
- The probe not being perpendicular to the anode surface
- The structure around the anode distorting the electric fields (eg if the structure is not symmetrical)
- Proximity to other anodes
The influence of such factors was explored in the paper and demonstrates how if, for example, measurements are not taken centrally on the anode, the data can nevertheless be used to estimate output.
To obtain further information, please contact us
BEASY once again attended the annual NACE Corrosion Conference, which this year was held in Nashville from March 24 - 28, 2019. We were active in both the conference program and exhibit hall showing our corrosion modelling services and software.
PAPER PRESENTED AT NACE
Predicting Cumulative Galvanic Corrosion Damage in Aircraft Structures using Environmental Exposure Measurements
By Robert Adey, Andres Peratta, John Baynham, Thomas Curtin
Andres will be presenting a paper discussing the material degradation mechanisms such as galvanic, pitting and crevice corrosion which limit the operational lifetime of aircraft and result in unsustainable long term maintenance costs.
Recent studies of naval aircraft suggest for example that galvanic corrosion is the primary corrosion mechanism, in nearly 80% of the cases, when corrosion damage is observed on the aircraft.
A new modelling methodology (Corrosion Service Life Model) will be presented capable of predicting the cumulative corrosion damage experienced by a structure using actual environmental exposure data (in this case collected on board a naval vessel). The approach is applicable not only to aircraft but to a wide range of structures subject to atmospheric corrosion.
Recent advancements in computational corrosion modelling tools have the potential to dramatically improve the durability of aircraft by providing engineers with predictive tools to improve material selection and develop more corrosion resistant designs. Corrosion modelling also provides engineers with forecasting tools that can be used to gain insight into the effect of long term corrosion damage; ultimately helping to improve maintenance scheduling and reduce fleet maintenance costs.
NEW PRODUCTS & SERVICES PRESENTED AT NACE
BEASY Corrosion Data Manager Services
BEASY Corrosion Data Manager enables engineers to manage and visualise in 3D CP survey data. Integrity management system do not fully meet the needs of the engineer responsible for corrosion as they do not provide access and visualizations of all the data the engineer needs to make fast and informed decisions. There is also often no easy way to see the trends in the data, or link the data to video and photographic data also recorded during the survey. BEASY Corrosion Data Manager provides access to all this information through a 3D visual interface to any member of the team.
The BEASY Corrosion Data Manager also provides the engineer with the ability to visualize in 3D the historical and predicted CP protection on the structure and the status of the CP system anodes.
BEASY Polarization & Corrosion Rate Prediction software is used by design engineers to quickly assess the corrosion risk of material combinations exposed to aqueous environments. Galvanic corrosion is one of the primary, and most costly, corrosion mechanisms observed when different metals and finishes are coupled. The BEASY Polarization & Corrosion Rate Prediction provides a more accurate, laboratory validated, method to predict corrosion rates based on the identification of crossing points for material polarization curves.
Galvanic corrosion is commonly assessed by comparing differences in metal potential (e.g. galvanic series in seawater table) with higher corrosion risk being associated with larger differences in metal potential. However recent research results obtained during development of the revised military standard, MIL-STD-889C suggests that potential differences do not fully account for the corrosion kinetics and can lead to wrong material compatibility decisions.
Given the high cost of corrosion maintenance many companies are searching for corrosion modeling tools to support the paradigm shift from “Find & Fix” to “Predict & Prevent/Manage”. The BEASY Polarization & Corrosion Rate Prediction software satisfies both designers, focused on material compatibility and coating performance who are concerned with new designs and retrofits for in-service vehicles, and maintenance engineers concerned with scheduling inspections to look for corrosion.
Cumulative Corrosion Damage
Predicting Cumulative Galvanic Corrosion Damage in Aircraft Structures
Robert Adey, Andres Peratta, John Baynham, Thomas Curtin
BEASY presented at the NATO AVT-303 Research Workshop on Corrosion Management Athens, Greece a new approach to predicting corrosion damage using computer simulation models. Not only the corrosion rate can be predicted for complex multi material structures but also the cumulative corrosion damage experienced by the structure during its service life. A demonstration of this new methodology (corrosion Service Life Model) was presented using environmental exposure data collected on board a naval vessel. The effects of crevice and pitting corrosion can also be included in this predictive model. The approach is applicable not only to aircraft but to a wide range of structures subject to atmospheric corrosion
For further information on the BEASY Corrosion Manager Software Contact us
Influence of Anode Location and Quantity for the Reduction of Underwater Electric Fields under Cathodic Protection
Y.-S. Kima, S.K. Leeb, J.-G. Kima,
School of Advanced Materials Engineering, Sungkyunkwan University and The 6th Research and Development Institute, Agency for Defense Development,Republic of Korea Published in Ocean Engineering 163 (2018) 476–482
Electric fields form around a ship due to current flow from cathodic protection (CP) systems, such as impressed current cathodic protection (ICCP) and sacrificial anode cathodic protection (SACP) Also, underwater electrical potentials (UEP), which can generate underwater electric signatures, may form even in the absence of CP systems due to galvanic corrosion between the hull (steel) and propeller (nickel aluminum bronze, NAB). A steady current flow around the hull of a ship can create an underwater electric field. Modern underwater mines are attuned to these electric field signatures and use them to detect and classify passing vessels. Thus, diminishing underwater electric fields is required to increase survivability.
To investigate the effect of anode location and quantities on the underwater electric fields, a number of simulations were performed to determine the design which minimised the electric field while maintaining protection of the vessel.
For further information on Cathodic Protection and Underwater Electric and Magnetic Signature Modelling
please contact us
BEASY Corrosion Manager Software enables engineers to quickly assess the risk to components and structures of corrosion and the effectiveness of surface protection systems. Galvanic Corrosion is important as it occurs whenever dissimilar metals or certain types of composites (eg carbon based) are located close to each other.
This major new release provides many new capabilities and enhancements and is the result of extensive research and development.
Typical applications include:
- Predicting the location of corrosion sites and assessing the severity of the corrosion
- Identifying the location and extent of corrosion protection measures required to prevent galvanic corrosion (e.g. coatings, paints etc)
- Improving designs by simulating the impact of material choices to minimize corrosion
- Assessing the impact of coating degradation and damage
- Simulation of the time dependent effects caused by change of coating breakdown factor or corrosion of surface finish which exposes the substrate
For further information on the BEASY Corrosion Manager Software Click Here
Some of the new features and enhancements are described below.
BEASY Corrosion Manager Software now provides the ability to model crevice geometries under uniform steady state galvanic corrosion. The model also allows the variation of the environmental conditions (electrolyte and polarisation properties) within a crevice.
Improved User Interface & Visualisation
To find out more about BEASY Corrosion Manager Software and the other corrosion simulation software and services we offer please contact us
BEASY will once again be attending the annual NACE Corrosion Conference, which this year is being held Phoenix from April 15th -19th 2018. We will be active in both the conference program and exhibit hall showing our corrosion modelling services and software.
We welcome you to come and visit our booth (No 1512) to find out more about the capabilities of BEASY simulation products, or how BEASY modelling services can provide the solutions you need. Alternatively to make an appointment to meet us at the conference, or to obtain further information, please contact us
Comparison of Resistance to Cathode with Resistance to Ground in the Marine Environment
By John Baynham and Tim Froome
John and Tims paper at NACE 2018 focuses on the calculation of Anode resistance which is a fundamentally important quantity which is used in all CP system design work in the marine environment.
Established methods for calculation of anode resistance determine the resistance through the electrolyte between the anode surface and ground (or “remote earth”), and are based on analytical or approximate formulas. Such formulas are generally based on simplified anode geometry, such as long thin cylindrical bars, and may include effects of interference between multiple such bars grouped in fairly simple geometric patterns. Resistance to ground of real anode shapes may be very different from formula-based predictions even for single anodes, and computer-based simulation methods are now available to determine resistance to ground both readily and more accurately.
To obtain further information, please contact us
Predicting Aircraft Corrosion
Atmospheric Corrosion Measurements to Improve Understanding of Galvanic Corrosion of Aircraft
Matthew Merrill, Mark Kim, Fritz Friedersdorf from Luna Innovations and Thomas Curtin, Robert Adey from BEASY
Fritz will present the paper at NACE 2018. Atmospheric corrosion represents an annual multi-billion dollar cost burden for the aerospace and defense sectors. For many aircraft, particularly those operating in marine environments, up to ninety percent of corrosion is due to galvanic interactions at dissimilar metal couples. As new materials are introduced with the acquisition of more advanced aircraft, galvanic corrosion is likely to remain a concern. The ability to model galvanic corrosion accurately holds out promise of being able to not only predict the performance of new material combinations and guide material selection but also to predict corrosion damage to optimize maintenance.
A segmented, galvanic sensor is presented that enables the quantification of spatial distributions of galvanic current under thin film conditions that can be compared to model predictions for verification and to judge the suitability of immersion versus thin-film electrolyte data inputs.
To obtain further information, please contact us