Materials Performance

MAR 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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Page 52 of 88

50 MARCH 2018 W W W.MATERIALSPERFORMANCE.COM COATINGS & LININGS ESSENTIALS Continued f rom page 49 Comin' home to means comin' home to... ...dependability, familiarity, a name you can trust A connection that has stood the test of time for more than 30 years. It's time to specify Lida ® for your groundbed. Comin' home to MIXED METAL OXIDE (MMO) ANODES FOR CATHODIC PROTECTION For more information visit or email BOOTH 538 CORROSION 2018 surprising and counterintuitive finding could have serious implications for the de sign of certain coating processes or for three dimensional (3 D) printing, which re quire materials to bond together and stay that way. When bonding two pieces of metal, either the metals must melt a bit where they meet or some molten metal must be introduced between the pieces. A solid bond then forms when the metal solidifies again. e research indicates, however, that under some conditions, molten particles bounce away in much less time than it takes for the surface to resolidify, and leave the surface while it is still molten. A revolutionary advance in the technol ogy for observing extremely high speed interactions, along with high speed imag ing, reveals that melting induced by the impact of metal particles can impede bond ing. e optical setup, primarily developed by MIT postdoctoral researcher David Veys set, includes a high speed camera that uses 16 individual charged coupled device (CCD) imaging chips and can record images in three nanoseconds. e camera is so fast that it can track individual particles being sprayed onto a surface at supersonic veloci ties, an accomplishment that previously was not possible. e team used this cam era, which can shoot up to 300 million The top row of photos shows a particle that melts the surface on impact and bounces away without adhering. The bottom row shows a similar particle that does not melt and does adhere to the surface. Arrows show impact sprays that look like liquid, but actually are solid particles. Photo courtesy of the researchers. frames per second, to observe a spray painting type of process similar to those used to apply a metallic coating to surfaces. While such processes are widely used, their characteristics have been determined empirically until now, since the process itself is so fast "you can't see it, you can't tell what's happening, and no one has ever been able to watch the moment when a particle impacts and sticks," comments Christopher Schuh, a MIT professor and member of the research team. As a result, there has been ongoing controversy about whether the metal particles actually melt as they strike the surface to be coated. e new technol ogy enables the researchers to observe what is occurring and study it, he says. If engineers find that a coating material isn't bonding well, they may be inclined to increase the spray velocity or temperature to increase the chances of melting. How ever, the new results show that melting should be avoided. e most effective bond ing occurs when the impacting particles and impacted surfaces remain in a solid

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