Papers and Presentations

How can we correctly simulate the evolution of corrosion damage in test systems, including different surface preparations, coatings and test environments? We implement fully 3D time-dependent Multiphysics CFD simulations on a multi-material structure along with the appropriate boundary conditions (polarization behavior of the materials involved) to predict an accurate variable film thickness distribution and calculate the appropriate galvanic corrosion using the Laplacian potential model. The ultimate objective of this work is to correlate numerical tests (real conditions) with Accelerated Corrosion Tests (ACT) such as such as ASTM B117 and G85 salt spray as well as a new Cyclic Relative Humidity (CRH) tests being developed by SWRI and NAVAIR. 

Julio Mendez, Engineer at Corrdesa Download Presentation

Electrochemical Machining (ECM) is essentially a high-speed corrosion process. It harnesses corrosion to machine very hard metals, thin sections and complex shapes, without the tool ever touching the workpiece. The problem is that the shape does not directly determine the dimensions of the final product, which makes it hard to design the tool for accurate production.

Fluid flow, hydrogen evolution, Joule heating and temperature gradients all affect the final shape. As a result, an Edisonian approach is typically used for designing ECM tools, which go through multiple design iterations to achieve the desired shape on the workpiece.

Our solution is to model the process using High-Performance Computing (HPC), efficient numerical algorithms and multiphysics CFD packages. In this approach, one of the primary remaining challenges is the large computational grid deformation required to model tool motion. This work shows a novel technique where the ECM is modeled using an efficient re-meshing algorithm that allows large deformation without incurring low mesh metrics and/or numerical instabilities.

The numerical predictions agree fairly well with CAD design specifications. This methodology is computationally more efficient than overset methods, although there are round off errors that diminish the beginning with mesh refinement in high-deformation areas.

Metal-filled coatings/primers/seals containing anodic materials are engineered to provide sacrificial protection to the underlying metal by the same mechanism as Zn, Cd, etc. The substrate is protected by an alloy pigment in the polymer coating that is electrochemically more active (anodic) than the material to be protected. In recent years, metal-filled coatings have been gaining an increasing share of the aerospace and defense market, in large part because environmental restrictions both in the US and particularly in Europe are driving the aerospace and defense industry away from the use of toxic Cr6+-containing primers that.

As with other complex materials, metal filled coatings have been developed by an Edisonian approach, which can now be replaced by accurate computational modeling to optimize the design of the anodic particles and the polymer matrix optimum performance. We have developed a novel Computer-Aided Engineering (CAE) model using Computational Fluid Dynamics (CFD) and a Discrete Element Method (DEM) to create a 3-D model of the metal-filled primer, that shows how it will interact electrochemically with the substrate and adjacent materials, allowing us to optimize it for different applications (corrosion control, wet install, gap filler, sealer, etc.).

For decades the aerospace industry has employed hexavalent chrome-converted cadmium coatings, primarily for sacrificial corrosion protection of high-strength steel components. Since Cd and Cr6+ are both highly toxic, manufacturers are replacing electroplated Cd with ZnNi. Because ZnNi is an alloy it is a significant challenge, as we now have to control, not only the thickness of the electroplated ZnNi, but also its composition across the entire surface of complex components for optimum performance and durability.

Fortunately, the science of electrochemistry can be used both to optimize the plating process and predict its corrosion protective performance. Using examples, this paper presents a workflow within a 3D simulation framework that enables a designer to develop a corrosion risk map of a component/sub-assembly, to optimize both the plating process and the performance of the coated component.

Alan Rose, CEO of Corrdesa Download Presentation

Engineers have long known that the old methods of corrosion prediction (e.g. galvanic tables) and testing (ASTM B117) are inadequate and inaccurate. New capabilities for computational corrosion prediction are improved in order to exactly understand how the corrosion occurs and how severe it will be; and with that information to design more durable systems. The aim of the session was to provide a discussion Forum to share information and ideas on corrosion modeling and testing so as to predict and minimize corrosion in complex systems. The Forum brought attendees up to speed with developments in the area of corrosion prediction and test development and raise awareness of changes in the MIL-STD-889 specification and how this will impact design methods.

  1. Victor Rodriguez-Santiago, Head of Corrosion and Wear Branch at NAVAIR. Download Victor’s presentation

This presentation will combine “Development and Validation of a Cyclic Humidity Corrosion Test” (SERDP-ESTCP Symposium 2018) and “Galvanic Compatibility Assessment: New Methodology and Standardization” (ASETS Defense Workshop 2018).

  1. Jim Dante, Manager of Environmental Performance of Materials at Southwest Research Institute. Download Jim’s presentation

This presentation will summarize “Cyclic Corrosion and Failure Mechanisms” (SERDP-ESTCP Symposium 2018).

  1. Kristen Williams, Senior Materials Engineer at Boeing. Download Kristen’s presentation

This presentation will summarize “Degradation and Failure Mechanisms of Protective Coating Systems” (SERDP-ESTCP Symposium 2018).

  1. Alan Rose, CEO/Principal Engineer at Corrdesa LLC. Download Alan’s presentation

Presentation title, “Using simulation to understand the difference between corrosion in atmospheric environments and chamber tests”.

The galvanic potential tables people have been using for years often give the wrong answer. Now the U.S. Navy is taking a new approach and updating MIL-STD-889, the galvanic corrosion standard, replacing galvanic charts and tables with corrosion rate calculations. What does this mean for industry?

Download from the Material Performance website

The Simcenter conference was very interesting, providing a great opportunity to learn more about the present software tools and also the trends in future development. One key takeaway for Corrdesa was the presentation on ‘Design Manager’ – this is a very powerful tool allowing easy setup of many simulations to more thoroughly explore the design space. So now we have changed out engineering workflow to think in more of a stochastic framework of many simulations and ranges of parameters instead of deterministic simulations of one scenario after the other. This approach really leverages the power of our computing cluster and provides much more optimum solutions to our clients. 

Alan’s corrosion simulation presentation was received very well with many questions and follow-up meetings. Much of the  Siemens Simcenter community were unaware of the existence of the electrochemical modules within CCM+ and in particular the advances made in corrosion prediction. The presentation is available below showing how the ‘1D’ approach of Corrdesa Corrosion Djinn can be leveraged to assess corrosion risks in materials selection and then further refinement made in more complex designs with the use of CCM+ employing the Corrdesa electrochemical database.

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The demand for lightweight design and better fuel-efficiency in the aerospace industry has reflected a significant increase in usage of more lightweight materials
such as CFC (Carbon Fiber Composite), titanium and aluminum alloys. Combinations of these dissimilar materials are often dictated by structural requirements that need to be fulfilled in the design. In an aircraft, these disparate materials are usually mechanically joined using fasteners or structural adhesives. However, when CFC and aluminum are connected, galvanic corrosion may be induced in the presence of moisture, introducing an additional degradation mechanism.

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Corrosion Djinn is easy-to-use software available on-line and as an ‘App’ for IoS and Android, that helps
engineers and designers make sound material choices in design and maintenance by predicting and
quantifying galvanic corrosion risk at material interfaces.

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The present approach for considering galvanic incompatibilities is simplistic and static. It is simplistic in
that the only thing it takes into account is the galvanic potential difference between two adjacent materials.An estimate of the galvanic corrosion severity is usually based on some form of galvanic potential table,
as in MIL-STD-889. However, in mixed material assemblies it is the galvanic current that determines the
severity of corrosion, not the galvanic potential, and the two are not directly related.

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Aircraft typically comprise multiple materials, each exhibiting unique electrochemical properties. When they are exposed to harsh marine and global environments, the difference in material properties can lead to severe galvanic corrosion, causing safety risks, costly repairs, and reduced readiness.

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This standard defines and classifies dissimilar metals and establishes requirements for protecting coupled dissimilar metals against corrosion with attention directed to the anodic member of the couple

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