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
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. 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. 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. 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. 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. 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
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
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. 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. 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
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. 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
