Why limit yourself to gray?

1. Electrochemical and chemical
finishes of stainless steel
Why limit yourself to gray?

2. Electropolishing
It is an electrochemical process that allows to decrease the surface
roughness. We can imagine it as a kind of "reverse plating".
Basically, we can remove the surface layer by dipping the piece in a
chemical bath and applying an electric current. The peaks are
rounded, making the surface smoother and more even. The final
appearance is slightly reflective, even if does not reach a mirror
polishing such as that obtained with mechanical procedures.

3. As for the other polishing
processes, this finish also
increases the corrosion
resistance and makes cleaning
easier. The treatment is also
able to remove small surface
cracks or burrs, and eliminates
small ferrous contamination.
Electropolishing can also be
applied to complex shaped
objects where other
techniques can not be used.

4. Electrolytic Coloring
This color effect is unique, because it does not use any kind of paint or pigment. The
surface film of chromium oxide that gives stainless steel its resistance is transparent. Its
thickness, as thin as a few atoms, allows light to pass easily. But if we increase the depth
of this surface layer, interference phenomena filter the light rays. Certain wavelengths are
absorbed and others are reflected, creating the distinctive colored effects. A similar
phenomenon can be observed in soap bubbles or oil stains. By changing the viewing
angle, the colors appear to change as well.

5. Austenitic steels are particularly suitable for this treatment. The
number of colors that you can get is bronze, gold, red, purple, green.
These color correspond to a superficial film ranging from 0.02-μm to
0.36-μm thickness. Ferritic steels, on the contrary, only acquire a dark
gray color.
Since there is no pigment, the color is not degraded by UV rays and
does not require maintenance. It is also resistant to mechanical
machining without chip removal, such as bending. Along the outer
edge of the bend, where the material is stretched, the film will
become thinner and the color will be less intense.

6. Since this surface layer is
transparent, the underlying
metal finish is important. For
reflective colors we will
necessarily start from a gloss
finish. Welding and thermal
cutting will damage the color, as
well as scratches and abrasives.
With embossed decorated
sheets, removing the color in
certain areas can generate
contrasting effects.

7. Burnishing
We can get the color black by
dipping the workpiece in a
chemical bath of sodium
dichromate. This process can be
applied to any type of stainless
steel. The surface is durable,
does not flake, is resistant to
heat light abrasion. Normally it
is opaque, but can be made
glossy by applying oils or waxes.

8. Acid etching
This artistic technique has been
used for centuries to decorate
metal plates. The surface is
covered with a resistant substance
that is removed in specific areas.
The piece is then dipped in acid,
which attacks the unprotected
parts. The contrast between the
exposed points and those left
intact creates a pattern. Paints and
electrolytic coloring can be applied
before or after the process,
depending on the desired effect.

9. Painting
The stainless steel does not
need to be protected with
paint, which only has aesthetic
reasons. In some cases, it is
applied to improve the
visibility. Steel can also be
purchased in pre-painted sheet
or coil. Often it is protected by
an adhesive film which is
removed after processing.

10. Enamelling
The workpiece surface is coated
with a mixture of ceramic
powder and baked in oven at
high temperature, where it melts
and vitrifies.

11. Physical vapor deposition
This technique allows to deposit very thin films of
material on a substrate. The coating material is
heated within a vacuum chamber until it
evaporates. The atoms are deposited on the
workpiece to be coated and form a uniform layer.
With this system you can apply various colors
that are very resistant and that do not change
with the viewing angle. The colors obtainable are
gold, bronze, rosé gold, blue, black, burgundy.
Specific treatments enhance specific mechanical
properties, such as hardness, friction coefficient,
resistance to scratches and wear.

12. Metallic coating
We can combine the corrosion
resistance of stainless steel with
the aesthetics of another metal,
such as copper or tin. The coating
is usually applied by galvanic
processes. This layer can be
damaged by scratches or wear
and tear, but the underneath
stainless steel is not affected.

13. Gasparini Industries s.r.l.
Via F. Filzi, 33
31036 – Istrana (Treviso – TV)
Italia – Italy
t (+39) 0422 8355
f (+39) 0422 835700
e info@gasparini.it
Codice Fiscale, Partita IVA: IT 04364470262 – REA: TV
343703
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