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 46 Nanotechnology Early in my career, ICCP anodes were primarily cast iron or graphite. These were soon joined by platinum-clad anodes that evolved from finding a sec- ond marketplace for niobium-copper cored wires that were being manufac- tured for use in magnetic resonance image (MRI) scanners for hospital use. These MRI wires were soon found to be excellent platforms for ICCP if the wires were coated with a thin layer of platinum. In what seemed like just a few more years, mixed metal oxide (MMO) arrived. MMO anodes typically involved using ruthenium oxide (RuO 2 ) or iridium oxide (IrO 2 ) either singly or in various combinations to coat a titanium substrate. Titanium oxide (TiO 2 ) has a similar rutile-type structure as RuO 2 and IrO 2 and similar ionic radii of Ti +4 (0.075 nm), Ru +4 (0.076 nm), and Ir +4 (0.077 nm) that allow the develop- ment of a tertiary solid solution that arguably could be considered an early form of nanotechnology. 7 Today, science and engineering periodicals are filled with discussions of nanotechnology. 8-9 Our understanding of nano-scale includes not just the manufacture of new products but our understanding of corrosion itself on the nanoscale. 10 On the proactive side, as we better learn how to assemble materials atom-by-atom, we will produce amazingly corrosion-resistant materials with a wide range of structural and thermal properties. Likewise, on the reactive side, it allows us to better understand why corrosion occurred in one location and not the other when on the macro-scale the two locations appear so very similar. Corrosion engineers are familiar with anodes and cathodes, but recent advances in development in battery anodes and cathodes may lead to bat- teries that will easily power CP systems in remote locations with unimagina- ble service lives. Perhaps our grandchildren may develop a means to redirect or capture destabilizing ions present in the environment and in the process assist with in situ repair of protective oxide layers, like those present on stainless steels. Cross-pollenating Cross-pollenating is another area that likely will produce advances. For example, corrosion can be a problem with guitars, particularly electric gui- tars. Although this is not a topic frequently addressed by NACE, perspiration from the guitar player can cause corrosion of screws securing the pick guards and even can cause corrosion of the pickups (pups). Microphones are transducers that convert mechanical sound waves travelling through the air into variations in an electrical signal that get sent to the amplifier and then the speakers. The pups on an electric guitar are not microphones but are magnet-based transducers known as a variable reluctance sensor. Pups detect changes in the proximity of ferrous material, namely the steel strings of the guitar, so stringing your electric guitar with nylon strings will not work well—pups are not microphones. Pups have a permanent magnetic core that is wrapped with thousands of turns of fine enameled copper wire. The fine enamel can age and start to flake. Add to that the close proximity of alnico or ferrite magnets, and it should be obvious to a corrosion engineer that perspiration could cause cor- rosion issues or result in partial short-circuiting of the pickup with a loss of performance. To protect the pups, some manufacturers employ just a wrap or two of electrical tape; others add an additional coat of enamel, lacquer, or epoxy to the outer face of the enameled copper wires. Still others use a mix of about 20% beeswax and 80% paraffin, melt the wax and then submerge the pup into the melted wax for 15 to 30 minutes or until the pup stops bub- bling from the wax displacing air voids between with layers of the copper wire and the magnetic core. Over time, potting the pups with wax provides longer protection than the others, and problems can be easily corrected by melting the wax, whereas pups that are potted in epoxy and develop

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