Post-Treatment: High
nickel-zinc alloy can be post treated with Hexavalent
Chrome Free Thick Film iridescent yellow, bright, blue,
olive drab or clear passivate as well as a high quality
colour fast black finish. Other post-treatments are
available including sealants, lacquers and oils for
specific requirements
such as enhanced corrosion protection and high torque
lubricity.
Corrosion
Protection: In
general, corrosion protection is a function of the
thickness of the deposit. The neutral salt spay test
is used to assess the performance of a finish on a
component. The test assesses the time before the onset
of corrosion to the coating itself, the formation of
white rust as well as the time before the onset of
corrosion to the component substrate material, red
rust. The tables below demonstrate some results from
an ASTM B117 5% neutral salt spray test applied to
a 5µm deposit. [top]
Neutral
Salt Spray - hours to red (white) rust |
Passivate type |
Conventional zinc |
High Nickel Alloy zinc |
| Clear |
100 (6-24) |
900 (240) |
| Iridescent Yellow |
150-200 (72-96) |
1500+ (1000) |
| Black |
120-150 (72-96) |
1500+ (500) |
| Hexavalent Chrome Free Thick Film |
300 |
1500+ |
|
Properties |
Conventional Zinc |
Standard Zinc Alloy |
High Nickel Zinc Alloy |
| Nickel % |
Nil |
5-8 |
12-15 |
| Vickers hardness (100g) |
90-130 |
200-250 |
400-500 |
| Weldability |
Poor |
Good |
Good |
| Thermal stability |
Poor |
Good |
Excellent |
|
