Replacing Hexavalent Chromium in Passivations on Zinc Plated Parts The use and benefits of passivations based upon hexavalent compounds, particularly on zinc plated parts, are well established and understood in finishing. Through the changing attitudes within society, the continued long-term use of this technology is under question and review. We examine the background and comment on the alternative strategies available that are most likely to commercially succeed . . . By Paul C. Wynn, Business Manager and Craig V. Bishop, Special Projects Director McGean-Rohco (UK) Ltd. TABLE I—Desirable Characteristics of CrVI Passivates • Prevents Oxide Formation • Provides Color • Slow corrosion in prototypic tests (eg. salt, spray, roof top, etc.) • Provides adhesion for organics (eg. paint) • Helps prevent corrosion of painted surfaces (eg. creep) • Conductive • Thin • Flexible • Lubricious • Easily applied • Stable for weeks or months • Durable • Resilient (repairs itself) • re-hydrated after baking • Coats in recesses • Easy to strip • Inexpensive equipment • Single tank • Inexpensive TABLE II—The CrVI Chromate Film (Olation Polymer) TABLE III—Biestek and Weber   mg / dm2 Cr CrIII mg CrVI / dm2 dm2 / 2g ft2 / 2g Cd Clear 1 30% 90% 0.27 7407 797 Zn Clear 1 30% 90% 0.27 7407 797 Al Clear 3 30% 80% 0.72 2778 299 Al Yellow 10 35% 70% 2.45 816 88 Zn Yellow 12 35% 70% 2.94 680 73 Cd Yellow 15 38% 70% 3.99 501 54 Mg Yellow 15 38% 70% 3.99 501 54 Zn Olive 23 42% 70% 6.762 296 32 Cd Olive 23 42% 70% 6.762 296 32