Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr
Issue link: https://emj.epubxp.com/i/109221
CORROSION This photo of a bearing part treated with NKE Austria's SQ171E coating shows that even after a salt spray test the coated part (front) does not show visible traces of corrosion, while the uncoated reference part (rear) shows traces of rust. more cost-effective, yet offers better anticorrosion protection. Meanwhile, according to results published recently from a joint university research project, a coating so thin it's invisible to the human eye has been shown to make copper nearly 100 times more resistant to corrosion, offering tremendous potential for metal protection even in harsh environments. In a paper published in the September 2012 issue of Carbon, researchers from Monash University in Australia and Rice 52 E&MJ; • FEBRUARY 2013 University in the United States said their findings could mean paradigm changes in the development of anti-corrosion coatings by using extremely thin graphene films. Graphene, a substance with atoms arranged in a regular hexagonal pattern similar to graphite, but in a one-atom-thick sheet, reportedly has a variety of potential applications, including lightweight, thin, flexible yet durable display screens, electric circuits, and solar cells, as well as for enhancement of various medical, chemical and industrial processes. It also is attracting research attention for its possibilities as a means of increasing metal's resistance to corrosion. "We have obtained one of the best improvements that have been reported so far," said study co-author Dr. Mainak Majumder. "At this point we are almost 100 times better than untreated copper." Dr. Parama Banerjee, who performed most of the experiments for the study, said graphene had excellent mechanical properties and great strength. The polymer coatings often used on metals can be scratched, compromising their protective ability, but the invisible layer of graphene—although it changes neither the feel nor the appearance of the metal—is much harder to damage. "I call it a magic material," Banerjee said. The researchers applied the graphene to copper using a technique known as chemical vapor deposition, and tested it in saline water. "In nations like Australia, where we are surrounded by ocean, it is particularly significant that such an atomically thin coating can provide protection in that environment," Banerjee said. Initial experiments were confined to copper, but Banerjee said research was already under way on using the same technique with other metals. Although the process is still in the laboratory-testing stage, Majumder said the group was not only looking at different metals, but also investigating ways of applying the coating at lower temperatures, which would simplify production and enhance market potential. While breakthroughs such as these are intriguing and offer the prospect of significantly enhanced corrosion protection for a variety of materials and equipment types, the most cost-effective solution for mining applications isn't always the most hightech method or product. On the following pages, author Joseph P. Langemeier offers a persuasive argument in favor of hot dip galvanizing—a process that was conceived and patented almost 200 years ago. www.e-mj.com