Chemical Resistance
Application Note for Liquid Flow Sensors

PrefaceThis application note provides information on the chemical compatibility of Sensirion’s liquid flow sensors.
Sensirion liquid flow sensors measure the flow completely media isolated through the wall of a straight flow
channel. This results in the best-in-class chemical compatibility to chemicals and aggressive liquids. For eachSensirion liquid flow sensor the list of wetted materials is provided in the respective datasheet.
Important Notice
The information provided in this document reflects the state of our current knowledge and theinformation available to us. However, compatibility with any liquid for any duration of exposure cannot
be guaranteed and it is in the user’s responsibility and best interest to test the sensor in the givenapplication.

Contents
1 Compatibility Table

22 Product Families

3

2.1 SLF3x Series .......................................................................................................................................................... 3
2.2 LD20 Series............................................................................................................................................................ 3
2.3 LPG10-1000 ........................................................................................................................................................... 3
2.4 Glass Capillary Based Sensors (SLI and LG16 series) .......................................................................................... 3
2.5 Stainless Steel Capillary Based Sensors (SLS-1500, LS32-1500)......................................................................... 3
2.6 High Purity Flow Sensors (SLQ-QTxxx) ................................................................................................................. 3
2.7 High Pressure Sensors (SLG-xxxx)........................................................................................................................ 3
3 Material Details

4

3.1 Stainless Steel........................................................................................................................................................ 4
3.2 Glass ...................................................................................................................................................................... 4
3.3 Polymers ................................................................................................................................................................ 4
3.4 Fluoropolymers....................................................................................................................................................... 44 Summary

55 Revision History

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6 Headquarters and Subsidiaries

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1 Compatibility Table

SLF3S

LD20

LPG10

SLI, LG16

SLS, LS32

SLQ-QT

SLG

PPS, Stainless steel, Epoxy

PEI, LCP, Epoxy

Glass

Glass or Quartz, PEEK, (FEP)

Stainless steel, PEEK, PTFE

Quartz, PFA, (PCTFE)

Quartz, Titanium, PEEK

Table 1 provides a list of chemicals that have been tested on the materials or researched in the literature.

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100%+++++++

10 - 100%2
10 - 100%
10 - 100%
100%
100%
100%

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o+++++++++oo+o+++/o+/o+o++++++++oo+o+

100%+o+++++

100%
100%
100%+++++o+++++++++++++++

Product Family

Wetted Materials

Type Chemical

Other

Organic solvent

Aqueoussolutions

NaCl (Sodium chloride)
NaOH (Sodium hydroxide)
HCl (Hydrochloric acid)
H2O2 (Hydrogen peroxide)
NaClO (Sodium hypochlorite)
Ca(ClO)2 (Calcium hypochlorite)
Ethanol
IPA (Isopropyl alcohol or 2-propanol)
Methanol
ACN (Acteonitrile)
THF (Tetrahydrofuran )DMSO (Dimethylsulfoxid )AcetoneTolueneHeptaneGasoline
Diesel fuelKerosene (Jet fuel)Mineral oil, Vegetable oil
Silicone oil
Engine oil, Lubricant oil+ : most likely suitable for long term usageo : possibly suitable for short/medium duration usage- : likely not suitable

Concentration
0.9%
1 M (=4%)
1 M (=3%)
30%
30%
32%

Table 1: Tested and/or researched compatibilities

1 stainless steel acts as a catalyst which dissociates H2O2 at high concentrations
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2 Product Families
2.1 SLF3x Series
The wetted materials of the SLF3x sensor series (including the SLF3S-1300F and SLF3S-0600F) are PPS(Polyphenylene sulfide), stainless steel 316L and an epoxy-based adhesive.
2.2 LD20 Series
The wetted materials of the LD20 sensor series (including the LD20-2600B and LD20-0600L) are PEI (polyetherimide),LCP (liquid-crystal polymer) and an epoxy-based adhesive. The LD20 is a single-use sensor addressing applications in
the medical market. No guarantee can be given for compatibility with any liquid or drug formulation. The user is
responsible to test the compatibility of the sensor’s wetted materials for his application.
To the best of our knowledge, we expect good compatibility with the following liquids: Water Saline solution
 Glucose solution
 Typical buffer solutions
Liquids that are known to be incompatible are:
 Strong acids and bases
 Acids and bases at high temperatures Acetone, THF, DMSO, Toluene
2.3 LPG10-1000
Owing to its design, the only wetted material of the LPG10-1000 is Borosilicate glass. No wetted adhesive is used in thefinal product. Chemical compatibility of the installed sensor is therefore usually limited by the customer’s manifold
material and by the sealing (e.g. O-ring) to this manifold.
2.4 Glass Capillary Based Sensors (SLI and LG16 series)
Glass capillary-based sensors house a straight capillary made from borosilicate glass or fused silica, fitted to the fluidic
ports made from PEEK. The internal seal is either direct (PEEK on glass) or based on the fluoropolymer FEP.
Refer to the datasheet for the type of glass that is used and whether a direct or FEP seal is used.
Solvents that soften PEEK (i.e. THF) can potentially reduce the integrity of the seal between the capillary and the fluidic
fittings, adversely affecting pressure ratings.
2.5 Stainless Steel Capillary Based Sensors (SLS-1500, LS32-1500)
Steel capillary-based sensors house a straight capillary made from stainless steel, fitted to the fluidic ports made fromPEEK. The internal seal between the fluidic ports and the capillary uses the fluoropolymer PTFE.
2.6 High Purity Flow Sensors (SLQ-QTxxx)
The flow sensors of the high purity SLQ-QT family use quartz glass and fluoropolymers as the only wetted materials.
Refer to the datasheet for the specific types of fluoropolymers used.
2.7 High Pressure Sensors (SLG-xxxx)
The sensors of the SLG series are designed for ultra-high pressure applications. The flow channel is made from fusedsilica and it is fitted to the titanium ports with a PEEK seal.

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3 Material Details
3.1 Stainless SteelStainless steel is inert to almost all solvents, alcohols, fuels and oils.
Grade 316 L stainless steel is a variant with good corrosion resistance to weak acids and many bases.
Grade 904 L stainless steel has a particularly good corrosion resistance to sulphuric and other acids as well as warm
salt water and other high chloride environments.
It is not possible to state precise compatibilities for stainless steel because they are highly dependent on the mixture, thetemperature and the concentration of the acid or base.
3.2 Glass
Borosilicate glass is widely used for components of laboratory instruments and is the dominant material for laboratory
glassware. It offers a high level of chemical resistance to water, acids, salt solutions, organic solvents and halogens.
Resistance to alkaline solutions is relatively good but strong alkaline solutions cause corrosion of the glass, as dohydrofluoric acid and hot concentrated phosphoric acid.
Fused silica (quartz glass) is used in the context of production lines and tool construction, due to its high resistance tosaline solutions, acids and water. Except for hydrofluoric acid (HF) and hot phosphoric acid (H3PO4), quartz glass is notcorroded by acids and acts neutrally against many other substances. The inertness of quartz glass to alkaline solutions
is better than of borosilicate glass and effects are only expected in the case of very strong alkaline solutions.
Hydrolytic resistance (DIN 12 111)
Resistance to acids (DIN 12 116)
Resistance to alkaline solutions (DIN 52 322)
(Class 1 is the best class in each classification)

Borosilicate glass 3.3
Class 1
Class 1
Class 2

Fused silica
Class 1
Class 1
Class 1

3.3 Polymers
PPS (polyphenylene sulfide) is a high performance thermoplastic. It is highly resistant to thermal and chemical stress.
PPS is resistant to most acidic and alkaline solutions and bleaches.
PEEK (polyether ether ketone) is chemically resistant and inert with most acids and bases. Due to its purity, high burst
pressure, chemical inertness and resistance it is used in the chemical processing industry and in analytical science
applications like HPLC. It has very good resistance to solvents and is very resistant to hydrolysis. It has limited
resistance to concentrated acids.
PEI (poly ether imide) is chemically resistant and inert to most acids and bases. It is closely related to PEEK, howeverwith reduced impact strength and thermal resistance.
3.4 Fluoropolymers
All used fluoropolymers (FEP (fluorinated ethylene propylene), PTFE (polytetrafluoroethylene, PFA (perfluoroalkoxyalkane), PCTFE (polychlorotrifluoroethylene)), have excellent chemical resistance to most solvents and most corrosiveliquids. It is rarely the case that the fluoropolymer is not compatible with any liquid that is compatible with the capillarymaterial.

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4 Summary
This application note summarizes the wetted materials used in Sensirion’s liquid flow sensors. Please consult thedatasheets for a list of wetted materials used in your sensor of interest.
The main characteristics of the materials used are also described. While choosing the wetted materials is part of arigorous development process, Sensirion cannot guarantee the fit to a specific application. It is the responsibility of thecustomer and the customer’s technical experts to check and assess the compatibility with any application-specificliquid. If questions remain, please contact Sensirion for support.

5 Revision History
Revision
321

Date
July 2020
Aug 2019
Feb 2009

Changes Chapter

Description

2.1, 2.2
AllAllAdded variants for the SLF3x and LD20 sensor series
Complete update
First version

Copyright© 2020, SENSIRION.
CMOSens® is a trademark of Sensirion.
All rights reserved.

6 Headquarters and Subsidiaries
Sensirion AGLaubisruetistr. 50
CH-8712 Staefa ZH
Switzerland

Sensirion Inc., USA
phone: +1 312 690 5858
info-us@sensirion.com
www.sensirion.com

Sensirion Korea Co. Ltd.
phone: +82 31 337 7700~3
info-kr@sensirion.com
www.sensirion.co.kr

phone: +41 44 306 40 00
fax:+41 44 306 40 30
info@sensirion.com
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phone: +81 3 3444 4940
info-jp@sensirion.com
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phone: +86 755 8252 1501
info-cn@sensirion.com
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phone: +886 3 5506701
info@sensirion.com
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To find your local representative, please visit www.sensirion.com/distributors

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