Cadmium
(Cad) is a bright silvery white metal deposit (as plated). Supplementary
treatments for type II can be golden, iridescent, amber, black, olive drab,
or clear. All enhance the corrision resistance of the coating. Corrosion
resistance is very good, especially with type II finish. The cadmium plating
shall be smooth, adherent, uniform in appearance, free from blisters, pits,
nodules, burning, and other defects when examined visually without magnification.
Luster: Unless otherwise specified,
the use of brightening agents in plating solution is prohibited on components
with a specified heat treatment of 180 Ksi minimum tensile strength (HRc
40) and higher. Either a bright (not caused by brightening agents) or dull
luster shall be acceptable. Brighteners may be used with alloys listed
in paragraph 3.2.8 of the specification. Parts which have been machined,
ground, cold formed, or cold straightened after heat treatment shall receive
stress relief bake in accordance with table I or Ia of the specification
prior to shot peening, cleaning or plating. All parts shall be baked within
4 hours of plating as specified in tables I of this specification. Baking
on types II and III shall be done prior to application of supplementary
coatings.
For Class 1 and 2 the minimum cadmium
thickness requirement shall be met after the supplementary treatment.
Excellent for plating of stainless
steels that are to be used in conjunction with aluminum to prevent galvanic
corrosion.
Cadmium deposits should not be used
when an alternate process meets the performance requirements of this specification.
Applications include:
fasteners; aircraft components; automotive
components.
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Cadmium |
[QQ-P-416F]
Type I: As plated.
Type II: Supplementary chromate treatment.
Type II plating shall not show white corrosion products of cadmium, pitting,
or basis metal corrosion products at the end of 96 hours (20%) salt spray
exposure per following table: |
Salt-Spray
Test
| Type |
Class |
Test
period for white corrosion products (hours) |
| Type
II |
Class
1 |
96 |
| |
Class
2 |
96 |
| |
Class
3 |
96 |
|
| Unless
otherwise specified, chromate treatment required for Type II is distinctly
colored iridescent bronze to brown including olive drab, yellow and forest
green
Type III: Supplementary phosphate
treatment. Type III shall conform to Type I of TT-C-490. Type III is used
as a paint base.
Class 1: .0005" minimum thickness
Class 2: .0003" minimum thickness,
additional thickness requirements are given in paragraph 3.3.1 amendment
2, of this specification.
Class 3: .0002" minimum thickness.
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