What is the purpose of this article?
Describe Rheonics sensor probes with Hastelloy C22 wetted parts for applications with highly corrosive fluids, material characteristics, and use cases.
What products are involved?
Rheonics inline SRV viscometer, and density and viscosity meter SRD.

Hastelloy C22 Material

The Hastelloy C22, or simply Alloy C22, is known for being a corrosion-resistant material, composed mainly of nickel, chromium, and molybdenum.

The Alloy C22 is used for a wide range of harsh chemicals in the industry including:

  • Chloride fluids (e.g. Calcium, ferric, magnesium, aluminum chloride)
  • Nitric acid - HNO3
  • Sulfuric acid - H2SO4
  • Hydrochloric acid - HCl
  • Oxidizing acid, etc. 

Some key characteristics of the Hastelloy C22 material are:

  • Composition: The nickel-chromium-molybdenum composition of Hastelloy C22 has an overall better performance and resistance than other Hastelloy variants (e.g. C276, C4, 625).
  • Corrosion resistance: Used in severe corrosive fluids (presence of acids, chloride, nitric, oxidizing fluids, etc.) even at high temperatures.
  • Application: Used in piping and pumping systems, general industry, automotive, chemical, etc. where exposure to corrosive fluids restricts the use of alternative metals (e.g. Stainless Stel 316, 316L, 904L)

Table 1: Hastelloy C22 Material Characteristics

Hastelloy C22 Material
NameHastelloy C22
DIN 2.4602

Nickel Ni 50-63%

Chromium Cr 20 - 23%

Molybdenum Mo 12 - 14%


PREN (Pitting Resistance Equivalent Number)
8.61 g/cm3

Rheonics Sensors with Hastelloy C22 wetted surface

Rheonics SRD Inline process Density and Viscosity meter, and SRV Inline process Viscometer are available with Hastelloy C22 material as probe's wetted part. This means that the material in contact with the fluid is Hastelloy C22, compatible for corrosive fluids and various acids. The back side of the probe including the connector keeps the Stainless Steel 316L (SS 316L) standard material.

The Hastelloy C22 probe variants enables the use of Rheonics inline sensors to measure density, viscosity and temperature, as well as related parameters such as concentration, of corrosive fluids and acids even at high temperatures without affecting the sensor operation, integrity and accuracy. This results in constant monitoring and tight control of the fluid’s properties.

Figure 2: SRV and SRD Long Insertion NPT 1.25” (SR-X5-Axxx-B1N25)

Rheonics Hastelloy C22 high corrosion resistance viscosity and density sensor probes are recommended when Stainless Steel 316L (1.4435) - the standard sensor probe’s material - is not compatible with the application fluids. 

Table 2: Benefit of Hastelloy over stainless for corrosive environments.

Compatibility of Hastelloy and Stainless Steel with corrosive fluids

Chemical Fluid
Stainless Steel 316L (1.4435)
Hastelloy C22 (2.4602)
Aluminum chloride
Ammonium chloride
Calcium chloride
Calcium nitrate
Chloric acid
Ferric chloride
Hydrochloric acid
Sulfuric acid

Chemicals compatibility with Stainless Steel 316L, Hastelloy C22 and Titanium Gr. 5.

The Rheonics sensor probes offered with Hastelloy C22 wetted material are shown in next table.

Table 3: Rheonics sensor variants offered with Hastelloy C22.

Sensor Code

Sensor variant with Hastelloy C22

Type-SR Sensor short probe with threaded connection, e.g. G1/2, 3/4” NPT
Type-SR Sensor short probe with custom connection, e.g. Flanges
Type-SR Sensor short probe with Tri-Clamp connection
Type-SR Sensor flush probe with custom connection, e.g. Tri-Clamp, Flanges
Type-SR Sensor long insertion probe with custom connection, e.g. Flange, API Hub, Tri-Clamp

Applications of Inline Density meter and Viscometer with Hastelloy C22

Some industries and applications where Rheonics Type-SR sensors made of Hastelloy C22 are:

  • Automotive industry: Density monitoring and acid concentration (e.g. sulfuric acid) on battery performance and production.
  • Brine, potassium chloride and water, and hydrochloric acid and hypochlorous acid.
  • Chemical Processing and Science: Brine for electrochemical cell with hypochlorous acid.
  • Chemical recovery.
  • Chemical crystalization.
  • Pharmaceutical: Ethanol distillation.  Acids and cleaning density monitoring.
  • Pulp and paper - ammonium Sulfite Mill.
  • Refinery Industry - coke refinery at vaporizer.
  • Water and wasterwater treatment.

Installation of Rheonics Hastelloy C22 Density meter and Viscometers for corrosive fluids

Rheonics Type-SR sensors have a simple installation process. The main requirement is to have the sensing area of the sensor probes correctly inmersed in fluid without dead zones as shown in next image.

Figure 3: Type-SR sensor probe's sensing element

For further installation considerations, visit next pages for each sensor:

Rheonics optional accessories for installation (e.g. flow cells for installation in 1” lines, weldolets, protection cages, etc.) are mostly manufactured in Stainless Steel 316L and are not offered as standard in Hastelloy C22 material. Enquire with sales team for available options. 

Plastic materials e.g. PTFE can be used as accessories for compatibility with corrosive fluids. 

How to order Rheonics viscometer and density meter made of Hastelloy C22 material?

How to order Rheonics Type-SR sensor with flange?


Rheonics SR- Type sensor

SRD: Inline Density and Viscosity meter

SRV: Inline Viscometer

SRD density meter and viscometer online RFQ

SRV viscometer online RFQ 


Wetted material 

Available variants:

C22: Hastelloy C22

SS: Stainless Steel 316L


Process Connection Configuration

Define the process connection from the options shown*. Probe variants compatible with C22 material are:

-X1: Threaded probes.

-X2: Short variant. Define flange with norm, size, pressure rating, etc.

-X3: Tri Clamp probes

-X4: Flush probes.

-X5: Long insertion variant. Define flange with norm, size, pressure rating, etc.

*Rheonics can keep adding new process connection variants.


Insertion Depth - “A” - If applicable

Only applicable for -X5.

The insertion length should be defined, this is the distance between the sensor tip and the flange. Probe wetted zone.


Process Connection "B"

Process connection should be defined by the user for all flanges with norm, size, pressure rating, etc.

Rheonics will then create the corresponding flange’s code.

Prefix “B” is only used for -X5 sensors.


  • 34N: 3/4” NPT
  • BD50CR: DIN Flange DN50 PN16 RF for -X5
Complete the RFQ with missing details (viscosity and/or density range, calibration accuracy, temperature rating, etc.), submit the form, and the Sales Team will contact you soon.