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www.restek.comGC ACCESSORIES |
GAS MANAGEMENT
Tubing
Available tubing coatings include:
•
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 tubing, 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 coated 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 deactivation 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-temperature applications
(>400 °C) cannot be chemically deactivated.
5. What are the temperature constraints of these surface treatments?
On stainless steel, a Silcosteel® layer is stable to 600 °C. Parts treated with a secondary
polymeric layer are limited to temperatures of 400 °C in inert atmospheres and 250 °C when
oxygen is present, the temperature maximums for the polymer. Temperatures above 600 °C
can be used under certain conditions—please contact us for information.
6. Why use Sulfinert® or Silcosteel® treatment instead of PTFE coating?
Three reasons: 1) Sulfinert® and Silcosteel® layers are nonpolymeric, so they do not
exhibit the problems associated with gas permeability. 2) PTFE coating often flakes off the
surface, while the Sulfinert® or Silcosteel® layer is tightly integrated into the substrate
lattice. 3) PTFE coating is limited to 280 °C, while Silcosteel®-treated stainless steel tubing
and fittings can be used to 600 °C.
7. Why use Sulfinert®-treated tubing for transfer lines?
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 mercaptans.
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
Sulfinert® Electropolished 316L SS
Sulfinert®
304 SS
Sulfinert®
316L SS
Silcosteel®-CR
Electropolished
316L SS
Low
Intermediate
High
ppm
ppb
ppt
Sensitivity range
Aggressive
Intermediate
Mild
Acidic corrosion
Pressure range
Restek Tubing Reference Guide
This chart will help
you determine the
tubing best suited to
your application with
respect to pressure,
sensitivity of your
analysis, and acidic
environment exposure.
frequently asked
question
Which treated
tubing should
I use?