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.

Crevice Modelling

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

Cathodic Protection

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

In early 2017 at the NACE Corrosion Conference in New Orleans BEASY staff presented some recent developments and applications in the technical sessions and exchange groups. It was great to meet many friends at the conference and discuss how modelling can be used to improve and optimize CP systems as well as providing further confidence in their performance.

Assessment of Effects of Cavities and Narrow Channels on CP Design in the Marine Environment

Underwater termination assembly, mud mat, split casing, armour
termination and bend limiters being readied for deployment.
Source

At this year NACE John Baynham and Tim Froome presented an interesting paper on the difficulties presented by the geometry of certain structures in obtaining adequate CP protection.
CP system design work in the marine environment makes use of structure surface area, required current density, and anode resistance formulae to select the number and mass of anodes required to protect a structure. These formulas do not take account of restrictions to current flow caused by close proximity of structural surfaces to each other, and consequently CP systems which have been designed in the recommended way may sometimes not protect parts of a structure.
This paper investigates the protection provided to the structure when cavities and narrow channels/annuli are present, and identifies patterns of behaviour. A series of computer-based parameter studies was performed in which, for example, separation between two structural surfaces is varied, and the extent of the protected area is determined. The paper also investigates effects of geometry on current flowing through a hole in a plate. This situation frequently occurs in design of mud-mats - when the interest is to determine current drain to buried surfaces, and sometime occurs when free flooding cavities need to be protected. Again computer-based studies are used, and for example the size of the hole is varied.

For further information please contact us

There were a number of papers published this year which featured BEASY modelling.

Optimization of the quantity, locations and output currents of anodes to improve cathodic protection effect of semi-submersible crane vessel

S.H.Xing, Y.Li, China University of Petroleum, Qingdao. H.Q.Song, Y.G.Yan, M.X.Sun. Luoyang Ship Material Research Institute, Qingdao

Potential profiles on SSCV after optimization for the different cases considered which represent the loading of the crane and the coating condition

In this paper published in the Journal Ocean Engineering a 3-D boundary element model of a semi-submersible crane vessel (SSCV) is combined with movement of anodes and adjustment of currents to optimize the anode quantity and location. The protection in four different states of the crane vessel representing the loading and coating condition were predicted and the simulation results indicate that the SSCV is well protected for the whole service life when the protective coating on the hull is repainted every seven years.

Paper Source

For further information, please contact us.

Optimization of the Cathodic Protection Design in Consideration of the Temperature Variation for Offshore Structures

M. S. Hong, J.-H. Hwang and J.H. Kim. Hyundai Heavy Industries Co., Ltd.,

Optimized simulation results of FPSO: (a) final stage at 5°C and (b) final stage at 28°C.
In this study published in Corrosion, electrochemical tests were performed to obtain the carbon steel (EH36; UNS K12821(1)) cathodic polarization curves which contained environmental information under tropical (28°C) and arctic (5°C) environment model conditions, and the surface morphology was analyzed after the potentiostatic polarization test using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS).

Based on the polarization data, a computational analysis was conducted to verify and optimize the CP design of the floating production storage and offloading (FPSO).

Paper Source

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BEASY is working on a project supported by the United States Navy Sea Based Aviation Program and the Air Force to validate and develop computational corrosion modelling tools which can be used to predict the location and severity of corrosion within aircraft structures. The increased use by engineers of corrosion simulation tools during design and maintenance has the aim of improving the durability of an aircraft through better material selection, improved corrosion resistant design, and better predictive maintenance schemes. Improved aircraft durability will ultimately reduce fleet maintenance and life-cycle corrosion costs. 

Experimental test configuration with an Aluminum plate connected to an Stainless Steel Plate.
The plates are segmented so that the distribution of current can be measured

The work is building upon the BEASY Corrosion Manager software and is extending this technology to predict the long term galvanic corrosion risk to structures. We envision that this modelling technology will support a radical change in design philosophy for aircraft and other vehicle structures by providing engineers with corrosion simulation tools needed for current and future corrosion challenges.

In conjunction with Luna Innovations Inc and the University of Virginia experimental tests have been performed to validate the galvanic corrosion models under "bulk" electrolytes and thin film conditions. For example good agreement has been obtained across a range of electrolyte film thicknesses comparing measured and model predictions of the corrosion current density distribution across a segmented electrode test specimen as shown in the figures. Details of this study will be published NACE Corrosion 2018.

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