RICHARD KAIL / SCIENCE PHOTO LIBRARY RICHARD KAIL / SCIENCE PHOTO LIBRARY
Machine oil on metal. Drops of fine machine oil on zinc plating. Oil is used in machines with moving parts as lubrication to help the parts move smoothly, and to reduce the amount of heat produced due to friction. The type of oil used depends on the machine, but is generally viscous enough to cover the parts, but not so viscous that it is unable to flow. Zinc-plating helps avoid the corrosion of some metals.
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