Materials Performance

OCT 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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OCTOBER 2018 WWW.MATERIALSPERFORMANCE.COM 38 (i.e., a decision based on corrosion protection, albeit corrosion resistance inherent to the alloy). In such a vein, the design of corrosion-resistant alloys is an area of active research. A "hot-topic" at the moment is so-called compositionally complex alloys (a subset of which are often termed high-entropy alloys) that have demon- strated exceptional corrosion resistance in aqueous and atmospheric condi- tions. 3 Such alloys are not yet optimized in terms of a complete property portfolio for engineering applications, but there is no doubt that future cor- rosion protection will be dealing with (i) new materials that are presently under development, and (ii) materials with inherent corrosion resistance being designed to be more durable—and not necessitating "traditional" cor- rosion control. I could add many more examples, but we can look no further from the present rapid uptake of additive manufacturing to produce net- shape components, from a range of new (and old) alloys, with disabilities that are only presently under study. Complex Systems The great unknown is the evolution of complex systems. If we went back 15 years (or less), most of us were not carrying around a laptop, let alone a smartphone. Yet now, the pervasive nature of new technology sees us all carrying items that are being used in a manner (and environments) for which such materials have not previously been used. In other words, as technolo- gies evolve (in general), it's very likely we will see more drones, more driver- less cars, and then a transition to perhaps flying cars…I paint this picture to emphasize that a flying car would obviously need to be light, and have a unique (cost-effective) pro- pulsion system, as we can't all afford a superalloy gas turbine. As such, we don't know precisely what we will be dealing with, but one certainty is that there will be many new materials and technology interruptions, and all will have ramifications in terms of corrosion control. In regards to complex systems, there are numerous ones that are also presenting the extremes of our capabilities in corrosion protec- tion. For example, the sequestration and transpor- tation of supercritical carbon dioxide (CO 2 ) (in the carbon capture and storage cycle) remains a sig- nificant challenge in the case of contaminated CO 2 ; whilst the renewable energy sector (which is not only coming but will be dominant in the next 25 years by all projections) presents durability unknowns in everything from solar thermal generation, to proposed grid storage solutions. Finally, I will also provide one example that combines both issues of leg- islation and complex systems, highlighting the complexity of future corro- sion control. In most nations, the United States being no exception, automotive emission policy (of which the state of California has amongst the world's strictest targets) means that lightweight material systems are now being integrated into automobiles. A recent study (2018) by Liu and co-work- ers 4 of General Motors reveals the extreme complexity of a contemporary mass-market automotive "body in white" (Figure 1), indicating that the dura- bility of an automobile relies on the durability of a multi-material system— with widely varying material types (and electrochemical personalities!). In summary, one thing that we should always remember, especially all of us corrosion engineers (a.k.a., "rust busters") is that engineering materials are all "anthropogenic"—in other words, man-made. As a result, their proper- ties, good or bad, are our doing. Consequently, we have the ability to create materials with durability in mind, and an increasing responsibility to do so on the basis of the planet's finite resources. In the future, for corrosion control, we need to be smarter! We also need to learn more from the past, and be more proactive in education. One alarming point that was raised from the most recent of the rotating national surveys on the cost of corrosion (the lat- est being recently published from a meticulous national survey in China, 5 is Figure 1. Mixed materials "body in white" for Chevrolet Malibu and Cadillac CT6. Image courtesy of General Motors and from reference 4. Reproduced under a Creative Commons Attribution 4.0 International License.

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