| HARDCOAT: |
| Q.
How is Hardcoat different from conventional Anodize? |
A.
The Hardcoat film is much thicker and denser than
conven-
tional Anodic films. These properties give the coating
far
greater wear resistance. |
|
|
| Q.
What is the standard thickness? |
| A.
The Military Spec dictates .002 as standard, but
thicknesses from about .0005" to .004"
may be called out. The higher thicknesses may not
be achievable on certain Alloys. |
| |
| Q.
How closely can tolerances be held? |
| A.
Typically plus or minus 20% of the nominal thickness,
but with repeat jobs of controlled alloy, temper
and surface finish, closer tolerances are definitely
possible. |
|
|
| ELECTROLESS
NICKEL |
| Q.
What is EN? |
| A.
An Alloy of nickel and phosphorus which is harder
and more corrosion resistant than nickel alone.
It is produced chemically (auto catalytically),
not with any external power supply as in conventional
Electro Plating. |
| |
| Q.
Does EN build up on edges? |
| A.
NO ! The beauty of EN is that it goes on uniformly,
wherever the solution can touch the part's surface
and be circulated, exacting dimensions can be held. |
| |
| ANODIZE |
| Q.
What is Anodize? |
| A.
Anodize is an oxide film, usually formed on aluminum,in
an electrolyte. Current is passed between the cathode
and the anode (work piece), through the electrolyte,
and a porous oxide film is formed on the work piece. |
| |
| Q.
Is Anodize conductive or nonconductive? |
| A.
It is considered a non- conductor when dry, and
is a limited conductor when wet, depending on the
nature of the liquid being used.
|
| |
| Q.
How can dimensions be controlled when tolerances
are tight? |
A.
This can be accomplished by a combination of
methods all of which
schould be worked out between the manufacturer and
the Anodizer
before production begins. The methods can range
from simply choosing
a very thin anodic film (if allowed), to a combination
of controls in manufacturing,
chemical preparation at the Anodizing shop, and
anodic coating thickness control.
As long as both the manufacturer and the Anodizer
are aware of what each is
doing, acceptable parts will be produced.
For general reference, the dimensional build-up
per side of a conventional
anodize is about 1/3 of the coating thickness per
side. So if a .0006" is applied,
a dimensional change of .0004"can be expected. |
| |
| CHROMATE
(IRIDITE, ALODINE, CHEM FILM) |
| Q.
What is chromate coating? |
A.
Chromate coating, Alodine, Chem film all refer
to a thin film formed chemically
on metals, which contain tiny amounts of chrome
compounds that act as
corrosion inhibitors. In addition to having good
corrosion resistance, they are
very good bases for paints or other organic coatings,
and for abrasive bonding. |
| |
| Q.
What specification can we use to call out for chromating? |
A.
Mil-C-5541 is the most frequently used. It has only
two (2) classes
Class 1A and Class3. Class 1A covers the heavier
coating weights
and these are usually pale to dark yellow, or yellow
to light brown. Class 3
is for low electrical resistance, and would be lighter
yellows or clear. These
have slightly lower coating weights. Aerospace Materials
Specifications can
also be used, AMS 2473 is roughly equivalent to
Class 1A and AMS 2474 is roughly equivalent to Class
3 |
| |
| Q.
Are dimensions affected? |
A.
Generally, no, but in some cases, the amount of
metal removal in a preparation
cycle might need to be taken into account. |
