| Prior
to all manufacturing of products, the metal
must be cleaned and processed prior to the
finishing.
Metals
are classified into three groups:
-
Ferrous (iron, steel)
-
Non-ferrous (aluminum, tin, zinc, copper)
-
Exotic (platinum, monel)
Processing
consists of altering the surfaces of the metal
to:
-
Resist corrosion, and
-
Increase adhesion of paint
Corrosion
resistance is accomplished by anodising aluminum
or plating ferrous metal with a nonferrous
plate. Some non-ferrous metals are milled
chemically. (Actual removal of metal by chemical
attack.)
Non-ferrous:
mostly aluminium
-
Anolding
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PHOSPHATISING:
Iron
Phosphatising
This is done by a chemical specialty with a phosphoric
acid base product. A uniform iron phosphate coating
is imparted on the metal. A typical iron phosphatising
processing line is: (spray or immersion)
-
Clean
-
Rinse
-
Phosphatise
-
Rinse
-
Dry
-
Paint
This,
of course, has exceptions in that extra steps
can be added. Sometimes the cleaning and phosphatising
is one step. Zinc phosphatising is exactly the
same except that the coating is zinc.
The
coating is also known as a "substrate".
It is important to realise that an acid pre-clean
is required because if an alkaline cleaner is
used, it will carry through to the phosphatising
bath and neutralise it, and precipitate the phosphates
to the bottom of the tank. Caution must be used
if an alkaline pre clean is used. We do not have
an acid based cleaner for phosphatising at present.
PLA
TING:
Again, this is primarily a surface coating for
corrosion resistance on a non-ferrous metal with
a nonferrous plate. Plastic is plated only for
appearance.
Non-ferrous
metals are also plated for corrosion resistance
and wear. (abrasion resistance)
Prior
to plating (chrome, copper, gold, etc.) the metal
is cleaned with HYDROC or an acid cleaner almost
always by an immersion bath. Typical process is:
-
Clean
-
Rinse
-
Clean
-
Rinse
-
Plate (acid bath) Chromic sulfuric, hydrochloric
-
Rinse
-
Dry
The
time involved is not very long, 10-40 minutes
in each bath. (varies)
PICKLING:
Usually
done to ferrous metals prior to application of
drawing oils or talc. Acid (heavy) bath that eats
the surface of the metal so that the compound
will stick.
Usually
an interim step to further processing.
ALUMINIUM:
All
aluminum products are either cast, stamped or
extruded. To erase metal forming marks the surface
is:
-
Cleaned - alkaline (buffered) or alkaline (etch)
-
Rinse
-
Etched (caustic)
-
Rinse
-
De smutted (chromic acid)
-
Rinse
-
Anodised (hard coat - duranodic)
Aluminium
is given a uniform oxide coating in the anodise
bath (sulfuric acid) with electric current running
to the metal, much the same as plating on a coating.
Most non-ferrous metals particularly aluminium,
are extremely sensitive to alkaline attack. Acid
is used on the aluminium as a processor mostly
as a "high speed buff' or brightener.
It
is important to realise that we are selling a
clean metal surface to be processed further.
If
the surface is not clean "water-break"
free, the substrate - phosphatise will not adhere,
the plate will not stick and the aluminium etch
will be uneven. Appearance and uniformity is critical.
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