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Survey Furthers Development of Corrosion Software Prediction Technology

NAVAIR and Aircraft Makers Express Need for More Sophisticated Tools

Corrosion impacts the safety, function, and readiness of military assets, costing the Department of Defense $22.5 billion each year, according to the DoD Corrosion Policy and Oversight Office. Specifically, for Navy and Marine Corps aviation, this totals $2.6 billion and results in an average of 25 days of corrosion-related non-availability per year for each aircraft on active status.

Corrosion is clearly an enemy for which we need better weapons, since it is estimated that 35 percent of corrosion costs can be avoided by implementing better up-front analysis and design. The corrosion engineer is at a disadvantage when compared to his colleagues in structures and aerodynamics who have access to powerful FEA (Finite Element Analysis) software tools that can predict structural loading and flight response on complex 3-D computational models. As soon as weapons systems are deployed, material characteristics change due to environmental effects. Consequently, coatings and paint systems will degrade and get damaged, but the corrosion engineer does not have a tool to assess the long-term effects of these forms of degradation on the aircraft materials.

"Because airframe designers have stress analysis software, what we as materials and process engineers need is environmental stress analysis software," noted Bob Guillemette, Sikorsky Aircraft Corporation Lead—Corrosion & Prevention Control. Indeed, there have been many developments in corrosion prediction technologies. However, the field is a complex one, entailing many different mechanisms of corrosion and a huge number of variables. So the military departments want to know—where do we invest our time and dollars?

As part of phase one of an Office of Naval Research (ONR) project investigating the feasibility and efficacy of galvanic corrosion prediction from 2011 to 2012, Corrdesa conducted a survey in order to help NAVAIR and aircraft manufacturers such as Sikorsky guide priorities, resources, and investments into the research and development of a corrosion software prediction technology, while also engaging with potential users of these tools.

Key Corrosion Survey Findings

The aim of the survey was to gauge the extent to which the corrosion community was using engineering software tools. Only seven questions were asked, in order to make the survey simple and encourage a wide response. A total of 9,809 questionnaires were sent by email, resulting in final responses from 183, amounting to slightly under two percent (not atypical for e-mail blast surveys). In fact, the result was highly positive, since it meant that in absolute terms, 183 people considered the survey interesting and relevant enough to respond to.

Overall, 70 percent of respondents currently rely on in-house expertise to assess the impact of corrosion on design; however, 83 percent said they would use corrosion prediction software if validated, 57 percent preferred a stand-alone package, and 20 percent stated that such a tool would have to be integrated within their company CAD environment.

The first question was a filter question to ensure that Corrdesa engaged with a relevant sample. Respondents comprising 10.8 percent stated that corrosion did not affect their products, but many of these still continued to answer remaining questions, because they comprised coatings and corrosion mitigation equipment providers. Essentially, corrosion affected their clients' products.

The common methods are mainly based on experiential information, such as best practices and the testing of prototypes. This is where we see risk, i.e., how can you be sure that future issues will be identified and predicted based on past experience?

The response to this question was provocative. There is a great deal of interest in the potential of corrosion prediction software tools, with 82 percent of respondents saying they would consider such tools, assuming, of course, that the tools were qualified and validated.

Underpinning this question was the recognition that the number of product engineers in an organization is disproportionate to the number of those with an acknowledged expertise in corrosion. For example, a large organization such as United Technologies might employ 15,000 product engineers who make many design decisions with corrosion implications, and apply work based upon corrosion engineering standards. Next, there might be around 1,000 materials engineers who "own" the actual corrosion engineering standards and work process. However, within such an organization, only 45 corrosion engineers might actually possess the specialist's knowledge to develop and validate tools for the standards practices, and the methods for obtaining data. Consequently, if developers create software tools for corrosion prediction, it is very important to consider how a user community would implement such tools. It might be the best and most accurate software in the world, but if an organization cannot see how it fits into their design workflow it will simply not be used. With this question in mind Corrdesa envisioned two model users;

  • the materials and process engineer who would be more familiar with corrosion fundamentals
  • the design engineer who would be more familiar with good design practice but not necessarily materials fundamentals

The materials and process engineer would probably use 'stand-alone' software, and the design engineer would use some type of CAD-integrated version. Among the survey respondents, two-thirds of those open to using corrosion prediction software would prefer access as a stand-alone tool. This result raised the following question: Does this preference indicate a desire to keep such tools within the control of the specialists? Maybe such a scenario could be a step along the way, and when the software capabilities and limitations have been clearly defined, there might be greater acceptance of a CAD-integrated tool. However, on further analysis, the survey revealed that individuals that preferred CAD-integration were generally from the larger, established organizations.

This question was more specific, in order that Corrdesa might understand where such a tool would be applied in order to deliver value to the design process. It seems that a major challenge is to quickly understand the impact of changes, a challenge that is understandable against a backdrop of new material/composite introductions and a substantial influence of growing environmental legislation that severely affects the choice of protective coatings. (An example is the industry's move away from cadmium to zinc-nickel.)

There are many corrosion mechanisms, and only some of them were mentioned in this survey. However, Corrdesa found it very interesting that galvanic corrosion was cited so highly. The physics of galvanic corrosion have been studied extensively, and it is believed that we can now predict the galvanic reaction behavior from our growing understanding of the physics and chemical processes underlying this phenomenon. Software tools already exist to predict galvanic corrosion on complex assemblies of mixed materials. There would be further value in clearly understanding the impact of galvanic corrosion, since it is believed that this mechanism is a precursor to 80 percent of the corrosion and fatigue issues experienced on naval aircraft. Indeed, other mechanisms cited highly were localized corrosion resulting from pitting and crevices.

Organizations heavily rely on expertise and established practices supported by testing when it comes to delivering corrosion-resistant designs. However, there is a substantial interest in adopting corrosion prediction software tools particularly for the top-cited mechanisms of galvanic, pitting, and crevice corrosion.

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