Nickel is one of the most abundant elements on earth. It is hard, yet malleable, magnetic at room temperature, and a relatively good conductor of electricity and heat. Most notably, nickel is highly corrosion-resistant, which provides for a variety of uses by industry. However, a surprising discovery by a team of National Science Foundation-funded researchers has found that nickel not only corrodes, but does so in a way that scientists least expected. Like a finished jigsaw puzzle, materials are made of interlocking pieces. Microscopically, nickel is made of aggregates of small, tightly packed crystals or grains. Corrosion preferentially attacks the joints, or "boundaries," between these grains. This phenomenon, known as intergranular corrosion, is a localized type of decay that occurs at the microscopic level, targeting the breakdown of materials at the edges of each of these boundaries, rather than at the outer surface of the material. As such, it weakens the material from the inside-out. Until now, scientists thought that one special type of boundary, known as a coherent twin boundary, was resistant to corrosion. Surprisingly, the team discovered that nearly all the corrosion in their experiments occurred precisely on these boundaries.
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