Zinc and zinc nickel plating

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Zinc and zinc nickel plating

  1. 1. ZINC and ZINC NICKEL PLATING Benefits and Uses
  2. 2. Zinc Plating Why use zinc plating? • Provides a barrier layer against corrosion to bare steel • Zinc is a sacrificial coating and will corrode (white corrosion) before the steel begins to (red rust) • Final product is cosmetically pleasing • Can be plated in either clear, yellow, black, olive drab, and many other dyed colors • Finish is uniform and very bright
  3. 3. Zinc Plating
  4. 4. Zinc Plating • Application of zinc plating • Electrochemical process that applies a thin layer of zinc metal to the bare steel surface • The plating can be either done in rack or barrel • Thickness of the plating is usually between .0002” and .0005”
  5. 5. Zinc Plating • Application of zinc plating • A supplementary chromate coating can be applied to provide additional corrosion protection • This provides the color to the plating and can be either hexavalent or trivalent chrome or a chrome free passivate • Sealants can used to increase resistance to white corrosion as well as modify and lower the coefficient of friction
  6. 6. Zinc Plating • Issues with zinc plating • Government Regulations • REACH and RoHS • Plating suppliers were required to provide alternative finishes that did not use hexavalent chromium • Existing finishes that were compliant did not provide the necessary corrosion protection • Great strides have been made to replace hex chrome and now a trivalent chromate in both yellow and clear is the industry standard • ELV was one of the first such clear trivalent chromates to be available and in use at Saporito
  7. 7. Zinc Plating • Issues with zinc plating • Industry Standards • Increased corrosion protection requirements • 10 years ago the standard was 72 hours to white corrosion and 240 hours to red rust when testing with a 5% neutral salt spray test • Standard requirements have risen to over 120 hours to white corrosion and 360 hours to red • Again the plating suppliers are having to find alternatives
  8. 8. Zinc Nickel Plating • Introduced as an alternative to Cadmium Plating • Government regulations on cadmium led to need in the industry for coatings that provide similar properties with environmentally safe products
  9. 9. Zinc Nickel Plating • What is Zinc Nickel Plating • Same process as zinc plating but both zinc and nickel are deposited on bare steel at the same time • Deposits range from 5% to 20% nickel with the remainder zinc • Can be processed in both rack and barrel • Chromate coatings can be applied to increase corrosion protection • Like zinc plating they are available in clear, yellow, and black • Sealants are available to reduce the coefficient of friction
  10. 10. Zinc Nickel Plating
  11. 11. Zinc Nickel Plating • Advantages of Zinc Nickel Plating • Hardness • Typical hardness value of the as deposited coating is 3 times higher than zinc plating • Corrosion Protection • Far and away the superior coating in terms of corrosion protection to both white and red corrosion • Can achieve a minimum of 750 hours to white and 2000 hours to red rust
  12. 12. Corrosion Protection of Coatings Red White
  13. 13. Zinc Nickel Plating • Advantages of Zinc Nickel Plating • Variety of Industries Serviced • Marine applications • Agriculture • High resistance to fertilizer • Automotive • Electronics • Corrosion products not as loose and voluminous as with zinc plating
  14. 14. Zinc Nickel Plating • Advantages of Zinc Nickel Plating • Throwing Power • Has excellent coverage in both low current and high current areas • This provides a very uniform coating on the most complex of shapes
  15. 15. Zinc Nickel Plating • Drawback of Zinc Nickel Plating • Appearance • Very functional coating but a difference in cosmetics from zinc plating • Due to addition of nickel in the deposit the clear coating has a lot of iridescent to it • However the black chromate is uniform and is superior to zinc trivalent black chromates
  16. 16. Zinc Nickel Plating
  17. 17. Zinc Nickel Plating • Drawback of Zinc Nickel Plating • Yellow Chromate • At this time the yellow chromate is only supplied in the hexavalent form • Only clear and black would be both REACH and RoHS compliant
  18. 18. Summary • Zinc plating has been around for a long time and provides a very good coating for most industries • Government regulations and industry corrosion requirements have outpaced existing zinc technologies • Zinc Nickel has been introduced as a suitable replacement for Zinc plating • Zinc Nickel provides maximum hardness and corrosion protection that is well beyond industry requirements
  19. 19. Questions? Email us at steve@saporitofinishing.com Call us at 708-222-5300

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