318
800-356-1688 or 814-353-1300
GC ACCESSORIES |
GAS PURIFICATION ESSENTIALS
Tubing
Available tubing coatings include:
•
Siltek®
—The ultimate passivation of treated surfaces, from glass to high nickel alloys of steel; ideal for sulfurs, automotive
exhaust testing or stack gas sampling.
•
Silcosteel®-CR
—A corrosion resistant layer that increases the lifetime of system components in acidic environments containing
hydrochloric acid, nitric acid, or seawater.
•
Sulfinert®
—A required treatment for metal components when analyzing for parts-per-billion levels of organo-sulfur
compounds.
1. Can treated tubing be bent?
Treated tubing can be bent into curves with a bend radius greater
than 1 inch for
1
/
16
-inch OD tubing, 2 inches for
1
/
8
-inch OD tub-
ing, or 4 inches for
1
/
4
-inch OD tubing. The treatment layer will
remain intact as long as the tubing isn’t stretched dramatically. If
tight bends are necessary, use a treated elbow union or bend
untreated tubing and send it to Restek for custom treatment.
2. Can compression fittings be used without crushing the
treatment layer?
Yes. The layer is thin and permeates the surface. It compresses
with minimal damage.
3. Is welding possible after treatment?
Yes. The coating does not interfere with the welding of two coat-
ed components. The coating is lost at the weld and in the heat
affected zones approximately 2 to 5 mm on either side of the weld.
4. Is any additional chemical deactivation necessary?
A Sulfinert® or Silcosteel® layer leaves few exposed active sites, so
there usually is no need for additional treatment. Chemical deac-
tivation is useful in chromatographic applications in which water
will be vaporized on the Silcosteel® treated surface, but is not
necessary for Sulfinert® treated surfaces. Parts used in high-tem-
perature applications (>400 °C) cannot be chemically deactivat-
ed.
5. What are the temperature constraints of these surface
treatments?
On stainless steel, a Silcosteel® layer is stable to 600 °C. Parts treat-
ed with a secondary polymeric layer are limited to temperatures
of 400 °C in inert atmospheres and 250 °C when oxygen is pres-
ent, the temperature maximums for the polymer. Temperatures
above 600 °C can be used under certain conditions—please con-
tact us for information.
6. Why use Sulfinert® or Silcosteel® treatment instead of
Teflon® coating?
Three reasons: 1) Sulfinert® and Silcosteel® layers are nonpoly-
meric, so they do not exhibit the problems associated with gas
permeability. 2) Teflon® coating often flakes off the surface, while
the Sulfinert® or Silcosteel® layer is tightly integrated into the
substrate lattice. 3) Teflon® coating is limited to 280 °C, while
Silcosteel® treated stainless steel tubing and fittings can be used
to 600 °C.
7. Why use Siltek®/Sulfinert® treated tubing for transfer
lines?
Siltek®/Sulfinert® treated stainless steel tubing offers all of the
advantages of glass or fused silica tubing for the transfer of active
compounds (e.g., sulfurs), but is far more durable and flexible.
8. Is treated tubing similar to glass-lined tubing (GLT)?
No. Sulfinert® or Silcosteel® treated tubing is flexible and can be
bent without heating. Also, the Sulfinert® or Silcosteel® layer is
highly inert, unlike impure glass.
9. How can I clean the surface of a treated part after use?
Most often, a mild organic solvent (methylene chloride,
methanol, hexane) or water is sufficient. Mild sonication may
assist and accelerate the process. Do not use caustic, abrasive, or
high pH (pH>8) cleaners, as they will damage or dissolve the
layer. Steam cleaning in the presence of oxygen or air could
create surface activity, and also should be avoided.
10. What materials should I avoid using with Silcosteel®
treated parts?
The Silcosteel® coating is silicon-based and is prone to attack by
hydrofluoric acid or by basic compounds. The surface should not
be exposed to media with pH>8.
11. Siltek® and Sulfinert®: What’s the Difference?
Siltek® is the name for the patented deposition process. When
the Siltek® process was developed, the application that showed
the greatest benefit was the storage and transfer of low ppb level
active sulfur compounds, such as hydrogen sulfide and mercap-
tans. Because there was (and continues to be) demand for a
reliable surface treatment for this application, the name
Sulfinert® is used to describe Siltek® treated products created
specifically for this purpose.
Tubing and Available Coatings
Restek sets the standard in tubing for analytical and process applications. Complete your system with precleaned or treated tubing
and treated fittings and valves for an inert, corrosion-resistant pathway.
Frequently Asked Questions
Website :
E-mail :
TelNo : 03 9762 2034 . . . in AUSTRALIA
Mar 2011
