Metal Finishing Guide Book


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Page 120 of 843

Figure 1. Periodic Table of Elements—note Zirconium's position. ceramic bake ware, or when fused as jewelry, cubic zirconia. Imagine cladding a reactive metal in an inert substance like cubic zirconia, then applying a corrosion- resistant organic coating. This is the promise of the modern transition metal coatings, once referenced as nano-ceramic. Figure 2 shows the relative thicknesses of the pretreatments. When gauging relative thickness of applied pretreatments, zinc phosphates are by far the heaviest and thickest pretreatments, depositing a mineral layer of some 1000 to 5000 nanometers (nm) in thickness. (Footnote 1) Iron phosphate applies typically a 250 to 500 nm thick coating. TMC pretreatments are approximately 50 nm, with some approaching 200 nm in thickness. They are the smallest, thinnest of the pretreatments, and are much thinner than the traditional metal phosphates they replace. Figure 2. Relative coating thickness of transitional metal coatings, iron phosphate and zinc phosphate. 117

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