Proceedings of the Materials Forum 2007: Corrosion Education for the 21st Century (2007)

An informal study assessing corrosion education within engineering curricula at our nation’s institutions of higher learning was conducted in 2004 by the Advanced Materials and Processes Technology Information Analysis Center (AMPTIAC), an information analysis center (IAC) sponsored by the Defense Technical Information Center. The results from that initial study were then employed by another DoD-sponsored IAC, the Reliability Information Analysis Center, to continue the analysis.

The informal AMPTIAC study was designed to support DoD’s emerging interest in corrosion by investigating whether inadequate coverage in undergraduate engineering curricula could be partly responsible for the current problem. The focus was on undergraduate education since most engineers responsible for developing, producing, and sustaining products do not seek advanced degrees.

When the study was complete, the presenter co-authored a white paper,¹ which DoD submitted to the Senate Armed Services Committee. That paper described the findings from AMPTIAC’s study and articulated the view that insufficient subject-matter knowledge and focus within engineering curricula lead to inadequate consideration of corrosion prevention and control during design. Without proper up-front design analyses, unanticipated and costly corrosion problems are far more likely to occur over a product’s life cycle than would otherwise be the case. In direct response to the congressional interest that was generated by the white paper, DoD’s Office of Corrosion Policy and Oversight sponsored the workshop and its outcome, the upcoming NRC study being carried out by the Committee on Assessing Corrosion Education.

Using U.S. News & World Report’s 2004 listing of top engineering schools as a guide, the curricula of 20 engineering schools were examined as part of the AMPTIAC study. These schools included the top 10 Ph.D.-granting universities and the top 10 4-year colleges. The universities included the Massachusetts Institute of Technology, Stanford, University of California, Berkeley, the California Institute of Technology, the Georgia Institute of Technology, the University of Illinois, the University of Michigan, Carnegie Mellon University, Cornell University, and Purdue University. The 4-year engineering schools included Embry-Riddle University, the U.S. Air Force Academy, St. Louis University’s Parks College, the U.S. Naval Academy, the Rose-Hulman Institute of Technology, Cooper Union, Bucknell University, the U.S. Military Academy, Cal Poly-San Luis Obispo, and Harvey Mudd College.

Two different courses of study were examined: materials engineering and mechanical engineering. Materials engineering was examined for its obvious focus on the development and behavior of materials. While design engineering encompasses many different specialties, resource limitations precluded an analysis

of all of them. For this reason, mechanical engineering was selected to be representative of the design engineering community.

Design engineering was included in the study because corrosion problems can often be traced back to decisions made during materials selection, a process routinely conducted by designers. Some industries such as aerospace, chemical processing, and oil production have active corrosion prevention and control programs that start early in the design process. Because of cost, safety, reliability, warranty, or product liability concerns; these industries have rigorous procedures embedded within their materials selection processes that are designed to ensure up-front consideration of corrosion. However, this is not the case for most industries and applications. It is the author’s belief that neglecting corrosion considerations during materials selection is the root cause of many problems currently seen.

A number of factors were investigated. These included whether the curricula included courses on materials selection and/or corrosion, whether corrosion was taught as part of another course, and if it was taught, whether it addressed both the mechanisms of corrosion and the processes for selecting corrosion-resistant materials and related protective technologies such as coatings.

Only 1 of the 20 mechanical engineering departments examined under this study, that at the U.S. Naval Academy, required a materials selection course. Three schools required a corrosion course: the U.S. Air Force Academy, the U.S. Naval Academy, and St. Louis University’s Parks College. These results seem to indicate that the U.S. military has taken some steps to increase its future graduates’ awareness of corrosion. Six of the schools studied taught corrosion as part of another required course, but only 3 of them taught the subject from the perspective of materials selection. The other 3 schools focused on the mechanisms of corrosion. It is the author’s belief that focusing on the mechanisms alone has limited value if no attempt is made to also teach what should be considered when selecting materials and associated coatings, platings, surface treatments, or other corrosion preventative technologies.

Of the 20 schools examined in this study, only 2 had materials engineering departments that required a materials selection course, and only 1 required a course on corrosion. Five departments taught it as part of another required course and 3 taught it from the standpoint of materials selection.

The purpose of the informal AMPTIAC study was to determine the content and focus of corrosion education at our nation’s top engineering schools. It was based entirely on an examination of online resources, so it is possible that some factors pertaining to specific programs were overlooked. Nonetheless, it seems reasonable to conclude that, overall, corrosion receives little attention in current engineering curricula.

The cost of corrosion can be significantly reduced, but only if a unified approach to corrosion education is developed and implemented. Doing this will first require identifying the stakeholders in corrosion and the role they play in product life cycle. Designers, materials engineers, and corrosion specialists are certainly part of this stakeholder community, but so too are the maintainers, system operators, buyers, and supporting technical specialists, including those responsible for reliability, manufacturing, and systems engineering. Just improving materials engineering curricula or focusing efforts on narrow constituencies will do little to reduce corrosion costs if there is no complementary effort to educate the other stakeholders as well.

A “unified approach” does not mean that all engineers must become corrosion specialists. Rather, what is needed is to develop a culture of corrosion-savvy engineers who correctly employ corrosion control technologies and, when appropriate, engage corrosion specialists. Design and other engineers could be taught using a modular approach, where bits and pieces of corrosion knowledge are taught over several subject areas so that when the students graduate, they possess the level of understanding needed to put corrosion prevention and control technologies to work at the appropriate points in a product’s life cycle. If successful, this approach will transform current practice so that corrosion prevention and control is built in, which will reduce the cost of corrosion across the board.

The Fontana Corrosion Center (FCC) at Ohio State University (OSU) has a long tradition in corrosion education. Mars Fontana was active at OSU starting in the 1940s. He might be considered the “father of corrosion engineering” because he was one of the first to apply the scientific principles being developed in the middle of the past century to practical engineering problems. He formalized the different kinds of corrosion, a critical step in the understanding of corrosion phenomena, and wrote the book Corrosion Engineering. This book and its later edition, with sections on the electrochemistry of corrosion added by N.D. Greene, were used around the world for decades to train corrosion engineers. The corrosion curriculum at OSU in the laboratory now named for Fontana follows this tradition. The FCC resides in the Department of Materials Science and Engineering (MSE), in which students are working toward B.S., M.S., or Ph.D. degrees. Degrees are not offered specifically in corrosion science or engineering, however, and corrosion courses must fit into the broader degree curricula.

Currently three courses in corrosion are offered by MSE: a senior undergraduate course, a general graduate course, and an advanced graduate course. The undergraduate course is required for undergraduate students specializing in metallurgical materials and biomaterials, and is a technical elective for MSE students with other specializations. Approximately 75 percent of MSE undergrads take the course. Each year a few students from other departments, primarily welding engineering, take the course, but students from mechanical and chemical engineering do not. The course involves both lectures and weekly laboratories. The goal is to provide the students with a basis for understanding corrosion, tools for measuring the corrosion rate, some knowledge of common corrosion phenomena, and a foundation for selecting materials based on their resistance to corrosion.

The graduate-level course is intended for any graduate student in MSE, and about 50 percent of the grad students take it. There is no weekly lab, but one lab session is arranged to give the students experience in a range of electrochemical corrosion measurement techniques. This course provides much more detailed fundamental information about electrochemistry and electrochemical kinetics than the undergraduate class. The phenomenological aspects of corrosion are also discussed in more detail. This course is offered for distance learning by students living far away. The lectures are recorded using a tablet PC and made available for asynchronous viewing.

The advanced graduate-level material is targeted at graduate students doing research in corrosion. The goal is to provide advanced theories of specific corrosion phenomena and promote critical reading and independent analytical skills. Student participation in discussions is promoted using a range of pedagogical techniques, and students are assessed in large part on such participation.

FCC faculty members are also very involved in a short introductory course on corrosion offered every year for professionals at Penn State University, and the center also periodically offers an advanced-level short course for professionals.

Two other universities with corrosion programs should be mentioned. The Center for Electrochemical Science and Engineering in the Department of Materials Science and Engineering at the University of Virginia (UVA) has a strong program in corrosion. Its course offerings and educational philosophy are similar to those at OSU. Because there is no undergraduate program in MSE at UVA, its undergraduate corrosion course is taken by students from a range of other departments. The University of Manchester in the United Kingdom offers an M.Sc. degree in corrosion control engineering. The 1-year program consists of nine taught courses and a research dissertation. The course offerings are more comprehensive than what is available at any U.S. institution.

This talk will review common practices in the undergraduate education of mechanical engineers and attempt to answer two central questions: (1) How are materials concepts integrated into the mechanical engineering curricula? and (2) Do materials topics cover corrosion? It will also attempt to identify best practices and to compare examples that represent the normal way of covering corrosion in a curriculum with examples that represent the most rigorous coverage.

A preliminary study of a diverse range of programs shows that the most common practice is to cover materials-related topics in two courses: (1) a typically mandatory “properties of materials” survey course and (2) a design-oriented course on fracture and fatigue, which if not always mandatory is in any case a very popular elective. These courses typically cover corrosion in a cursory manner, not in any detail. To complement these two most common courses, a number of institutions offer materials electives that either (1) cover materials from a broader perspective that has a less “constitutive behavior” emphasis than specialized courses in mechanical engineering or (2) are specifically focused on corrosion. Judging from the admittedly limited survey, MSE-oriented courses are popular electives for mechanical engineers, although not many students are enrolled in specialized corrosion courses, possibly due to the infrequency of their offering.

In a tangential way, a limited number of materials-related issues are raised in other courses related to design and fabrication. An emerging trend appears to be integration of the topic “materials selection in design” into a survey course. Another way is keeping it as an independent elective for students in the “solids track” of mechanical engineering. This is often done using the material selection maps pioneered by M.F. Ashby. This approach (that is, Ashby’s text) addresses corrosion in a qualitative way; there does not appear to be a quantitative framework for materials selection. Nevertheless this trend may represent the best opportunity to integrate corrosion education with design.

With regard to the content of usually mandatory survey courses designed to familiarize mechanical engineering studies with materials science, corrosion is not commonly addressed. The reason appears to be the breadth of materials science and the limited number of course hours into which an increasingly broad curriculum must be fitted. Two compounding factors are (1) such courses are typically taught by faculty with expertise in mechanical behavior as it pertains to failure and design—that is, faculty with limited exposure to corrosion, and (2) the chosen text has treated corrosion in a rather limited way or not at all. The next section reviews a half-dozen or so commonly used texts in terms of their corrosion content.

The following texts are listed in order of corrosion content, from most to least:

• J.P. Schaffer, A. Saxena, S.D. Antolovich, T.H. Sanders, and S.B. Warner. 1999. The Science and Design of Engineering Materials, 2nd ed. WCB/McGraw-Hill, “Materials–environment interactions,” pp. 614-661. Seems like an excellent introduction to the fundamental mechanisms. Aside from one table summarizing polymer resistance to inorganics (bad, good, excellent), nothing on materials selection. Direct dissolution mechanisms, electrochemical corrosion-half-cell potentials, kinetics of corrosion reactions, types of corrosion (e.g., uniform, galvanic, pit/crevice, H-embrittlement, stress-assisted corrosion), gas-solid interactions, friction–wear, radiation damage.

• L.H. Van Vlack. 1982. Materials for Engineering: Concepts and Applications. Addison-Wesley Publishing Company, “Materials in hostile environments,” pp. 428-462. Very broad and descriptive coverage of basic corrosion concepts. Corrosion reactions, polarization, passivation,

stress corrosion, corrosion control (protective surfaces, cathodic protection, avoidance of galvanic cells, stainless steels). Concludes with high-temperature mechanisms (creep, oxidation, decarburization), refractory metals, materials at subnormal temperatures.

• C.R. Barrett, W.D. Nix, and A.S. Tetelman. 1973. The Principles of Engineering Materials. Prentice Hall, “Environmental degradation of materials,” pp. 179-189. Brief introduction to chemical mechanisms of corrosion and corrosion-related effects on materials. What it lacks in depth it makes up for in conciseness and accessibility at the undergraduate level. Topics: polymeric materials, metallic oxidation, metallic corrosion (electrode potentials, galvanic series).

• M. Ashby and D.R.H. Jones. 1996. Engineering Materials I, 2nd ed. Butterworth-Heineman, Part F: “Oxidation and corrosion.” Includes section on oxidation of materials and case studies in dry oxidation and in wet corrosion.

• J. Shigley and C. Mischke. 1989. Mechanical Engineering Design, 5th ed. McGraw-Hill. One-paragraph discussion of corrosion effects on endurance limits.

• D.R. Askeland and P.P. Phule. 2004. Essentials of Materials Science and Engineering. Thomson Publishing. One paragraph.

Corrosion is a key degradation mode that can occur in jet engines. It is rarely the primary cause of failure for a structural component, but it can accelerate other failure modes, such as fatigue. The corrosion process of interest varies considerably depending on the environmental conditions, such as temperature. At the lower temperature end, aqueous corrosion can manifest itself as galvanic corrosion, stress corrosion cracking, etc. Above 590°C (1100°F), hot corrosion can occur by means of deposits (salt, debris, upstream engine products, etc.) that electrochemically react with substrate materials.

Because corrosion can lead to high maintenance and repair costs, GE Aviation has developed design practices and procedures to apply the large knowledge base from test data and past results to guide the design and selection of materials to avoid corrosion-induced failures. Materials application engineers make the final selection of the materials, which can include coatings. A team of senior design and materials experts reviews these selections when they involve major components. While past experience guides new designs, there is imperfect knowledge of the environment that will be experienced by new engines or by new engine users. For instance, there are differences in the ways airlines operate their engines that affect temperature gradients in those engines; in the locations where airplanes are based; and in the chemistry of the fuel used. All of these factors and others add uncertainty to analyses regarding the potential for corrosion.

Undergraduate courses in materials, mechanical engineering, and chemical engineering generally touch only briefly on corrosion, and mostly on aqueous corrosion at that. A few universities have faculty members with expertise in hot corrosion who incorporate that topic into their course material. But it has been our experience at GE that undergraduate courses typically contain few practical examples of corrosion, and students have little hands-on experience with it (hot corrosion particularly) until their first job. Furthermore, we rarely find new graduates who have a real understanding of corrosion.

GE Aviation uses its experts to teach a number of technical courses to new engineers. Corrosion is covered in these courses, primarily from a heuristics viewpoint. The courses are open to all engineers and mandatory for all new materials engineers. They are relatively popular, and many design engineers have taken them:

• There are several sessions on corrosion in the failure analysis course. It uses real-world examples, and it contains broad guidelines for avoiding corrosion in its introduction to design practices.

• The superalloy course offers a rationale for the chemistry of the alloys that GE uses and teaches GE’s experience in alloying to minimize corrosion.

• The coatings course goes into great detail on the mechanisms of hot corrosion, with many examples of what has occurred and how the problem was mitigated.

GE addresses these critical tasks in designing and supporting its hardware:

• Design to avoid corrosion,

• Recognize corrosion in fielded hardware when it occurs, and

• Develop and qualify improved field actions and design changes to mitigate corrosion.

Material application engineers use their experience and design practice guidelines to select materials that will avoid corrosion. Senior engineers with the department who are experts in corrosion provide advice and guidance to new engineers. This approach works particularly well when the design conditions resemble past experience. When conditions are dissimilar, estimating the potential for corrosion can be challenging. Models that can quantitatively predict hot corrosion performance of materials under severe environmental conditions would be quite useful.

The recognition of corrosion once it occurs in field hardware is generally excellent. A knowledge base that would support the accurate prediction of the effectiveness of various mitigation strategies is a significant need. Similarly, qualifying a design change is also a challenge since accelerated laboratory tests for hot corrosion do not correspond directly to field conditions, so that qualifying design changes can become an expensive, lengthy trial-and-error process.

The ideal situation would be for a few universities to have well-funded research programs that extend the fundamental knowledge surrounding aqueous and hot corrosion. The faculty could then incorporate this knowledge into its materials curriculum. In any event, more attention should be devoted to the teaching of corrosion fundamentals, including hot corrosion, in the undergraduate curriculum. The teaching would be done not only in specialized courses but also in the context of materials courses that teach other mechanisms that degrade materials, such as fatigue and creep.

During the design phase there is always the pressure of schedule and of cost to design. Designers must only prove that a concept works; life-cycle costs are of little concern for many of them. Even good designers can have limited exposure to the optimum selection of materials. Consideration of corrosion during the design phase is rare in a number of industries, and some design engineers are not even aware of corrosion. Perhaps there are several reasons for that.

Several universities do not offer any corrosion classes for design engineers, leaving them little or no chance of learning anything about corrosion during their college education. The few who had an opportunity to attend a corrosion course may have learned only about what was relevant to their teacher’s work in research and theoretical fields.

Industry does not always have experts at hand who can help a design engineer to plan for corrosion, resulting in little chance for them to learn about it during their working life. Corrosion education is not considered “jazzy” and often does not feature in a corporation’s work plan. Add to this the fact that many times a company’s corrosion expert may have had no formal training in corrosion science and engineering—for example, a chemist may accidentally become a corrosion expert. Notwithstanding those in industry who have become highly qualified technical professionals through a process of lifelong learning, it remains that many in industry and elsewhere do not know what they do not know.

Those who are exposed to some practical aspects of corrosion and design guidelines for managing corrosion come to realize corrosion’s significance. Typically they say “I didn’t know corrosion could be that significant” or “Why don’t the universities teach corrosion to design engineers?”

Once in a while corrosion becomes evident during testing and failure analyses. The cost of redesign efforts is not well documented, nor is the full impact of losses due to corrosion known. For a design engineer to benefit from information about managing corrosion, the information must be simple, easy to understand, and precise.