Hydrosteel 6500

World’s first multipoint hydrogen flux corrosion monitor.

For easy reliable measurement of flux in extreme environments.

Flux monitoring…

Since the year 2000, Hydrosteel® has been recognized as the simplest and most effective way to monitor hydrogen flux through steel in petrochemical service. Hydrosteel works by the magnetic attachment of a flexible metal plate onto a pipe or vessel. Air is drawn between the plate underside and adjoining steel surface, capturing hydrogen flux exiting the steel.  The sample stream is passed over a hydrogen sensor.  From the sample gas flow, capture surface area, and increased hydrogen gas concentration in the air, the hydrogen flux is calculated and displayed.

…just got better

Hydrosteel 6500 delivers the simplicity of measurement of the original handheld tool, with months of battery operated monitoring capability.  Four separate sample lines ensure complete confidence in measurement integrity, so that the flux signature of a corrosion scenario is fully evident, and measures to mitigate corrosion and completely realized.  The new Hydrosteel comes a new probe featuring more reliable attachment and wider temperature tolerance.

Unique capability

Flux measurement uniquely measures an active effect of corrosion of service steel. Unlike wall loss measurements, the sensitivity of flux measurement is not limited in sensitivity by tiny decreases in thickness.  Unlike corrosion coupons and corrosometers, it indicates corrosion of the actual service steel, not a measure of corrosivity of a process fluid.

At low temperatures, the flux is generated by corrosion involving hydrogen promoters such as sour gas and HF.  Flux provides a real time indication of active sour corrosion and the risk of hydrogen induced cracking (HIC) caused by such corrosion.

At elevated temperatures, flux is associated with naphthenic acid corrosion.  Flux monitoring is also used to confirm the completion of hydrogen bakeouts.

Hydrosteel 6500 has been designed to serve the diverse applications of flux monitoring.

Sour corrosion control

H2S or ‘sour’ corrosion of equipment in oil and gas service costs billions in loss of plant integrity,  lower process throughput, risk management or corrosion control.  Often sour corrosion is suppressed by corrosive scale.  If corrosion is contingent on scale removal, or occurs in such acid environments that scale does not form, then hydrogen flux indications provide a unique opportunity to verify the effectiveness of sour corrosion control and optimize chemical treatments.  Routine flux measurements are carried out on sour pipelines, refinery distillation and HFCC unit overheads (eg condensers), typically by routine inspector visits to AT-S probes.  More episodic corrosion arises from amine units (undersalt deposits), and batch processes such as water washes and pH adjustment.  Trouble shooting is recommended  with the Hydrosteel LR probe.

HIC risk monitoring

Hydrosteel 6500 measures hydrogen flux through steel whose temperature and thickness can be readily verified.  With this information it is possible to calculate precisely the hydrogen activity generated at the corroding steel surface.   This provides a quantitative measure of hydrogen induced crack (HIC) risk.   By means of flux monitoring it is therefore possible to quantify the conditions that lead to HIC, and to establish a strategy for HIC avoidance. Use AT-S probes probes for routine inspection monitoring.  Carry out unscheduled tests with new LR probe.

Naphthenic acid corrosion monitoring

At increasing temperatures, hydrogen more freely permeates steel, and all types of acid corrosion are prone to generate hydrogen flux.  Flux from naphthenic acid corrosion in atmospheric and vacuum distillation units, can be used to estimate corrosion rate, offering the prospectus for a measured .  Oil feedstock blends typically vary every few days.  Flux monitoring provides a good indication of the blend’s corrosivity, and therefore offers a near real time prospectus for assessing oil feedstock corrosivity, complimenting the information provided by corrosion prediction algorithms. Also used in coker plants.  Use at least two AT-S or HT-S probes  plus background, monitor 3 data per day.  Trouble shoot with SR-probe.

HF corrosion monitoring

HF corrosion is attended by a robust hydrogen flux indication.  The method is used to monitor HF alkylation unit corrosion and provide an early warning of emergent corrosion issues, for example, from acid runaway. Use at least one AT-S probe plus background probe, monitor 3 data per day.

Hydrogen bakeouts

Hydrosteel flux measurement provides direct confirmation of sufficient hydrogen out gas of equipment that has been in hydrogen promoting or high temperature high pressure hydrogen service evidence an indication of corrosion in near real time.  This is carried out in a pre-weld hydrogen bakeout.  Typically three or four HT-S probes are deployed during the lay out of heat treatment circuitry.  Hydrosteel 6500 enables continuous sampling of such probes during the course of bakeout, enabling an up tod date assessment of bakeout progress and completion.

Sour corrosion lab testing

Sour corrosion experiments are widely undertaken, in the pursuit of chemicals, steels and processes which minimize both sour corrosion and its promotion of hydrogen induced damage to susceptible steel.


  • Full back-compatibility with previous Hydrosteel probes via conduit terminal.
  • Ruggedised field analyser with program operation and data monitoring capability [1].
  • New 150 mm high sensitivity LR (large roaming) probe, accommodating curvature down to 5 in and steel temperatures to at least 350 oC (2)
  • New 60 mm low sensitivity probe [3] for inspection ports engagement.
  • Steel clad flexible sample conduit [4] – up to 10 m length
  • Battery charge connector. Battery charging takes 24 hr, sufficient for a few days spot monitoring, up to 3 months long term monitoring [5].
  • USB connector [6] for data download and program upload. Monitored data downloaded as .CSV file.
  • Robust push button finger operation [7]
  • Large display with backlight [8]
  • Provision for wireless communication and networking [9]
  • Four ports [10] for sequential flux monitoring – appropriate for hydrogen bakeouts and multipoint measurements including background hydrogen
  • Staubli® connectors [11] afford easy pneumatic fitting to ports. Connectable to all original Hydrosteel probes
  • ATEX certification to intrinsic safe design to be confirmed.


Resolution 2 pL/cm2/s
Accuracy Resolution or +-10%, whichever is greater.
Response 90% in 90 s
Flux range 1 to 2,000 pL/cm2/s


Size and weight 320x185x90 mm, 4.1 kg without leather case.  4.45 kg with case.
Safety Initial Intrinsic safety narrative for IEC-ex.
Ingress Designed to IP 66
Portability Leather harness for analyser,  spot probes and conduit.
Battery Two 4.8 A.hr Li-ion batteries of rectangular construction at 3.8 V nominal to intrinsic safe design
Calibration Concentration: 100 ppm hydrogen. Flow:self calibrating.
Gas fittings Staubli® RBE3
Conduit 3 or 6 m, quick fit connections to case.
Probes LR probe, 150 mm diameter.

SRprobe  60 mm diameter

Keypad Panel mount IP rated buttons around LCD
Lights Backlit display only
Software One single standard software version is required for each kit.  All upgrades and data transfer achieved via USB connection. Customer configuration via key pad or USB.
Comms USB 2.0, enabling data transfer, programming and software updates.  Design for 2.4 GHz w ireless with proprietary protocol for communication to DCS, and an external vandal proof mushroom type or other aerial.
Options Data log and monitoring frequency from 1 Hz to 1 reading / day, monitoring station sequence etc.
Display 27 cm2.  Iconographic menu.  Battery reserve, programme selection, read out selection, etc
Memory 2 Gbytes data on internal SD card
Components Harness supporting analyser, LR and SR probe, background probe, 3 m conduit

Portable application

Hydrosteel 6500 is provided with a leather jacket carrying the analyser, both at-A and AT-B probes and conduit. The jacket is designed to be easy to carry, whilst protecting the apparatus from damage.

Application scenarios

Scenario 1: unscheduled spot measurements and short term monitoring

Hydrosteel is very well adapted for troubleshooting and monitoring of unexpected process upsets or corrosion episodes. After using the device to corrosion hotspots, the operator selects from the instrument a default monitoring cycle at 10 min intervals.

Scenario 2: scheduled spot measurements

AT-S probes are pre-fixed on the steel at, typically, typically 10 to 15 locations in a refinery unit.  The instrument is used for repeat spot measurements, say 3 per week, at each site.  After each spot measured flux and zone is stored in the instrument log by the user.

Scenario 3 scheduled monitoring

At-S probes are pre-fixed at up to three sites within a few metres of each other. Stanchions may be required for the instrument, placed in a metal box for protection.  The instrument is connected to the probes with conduit.  It is programmed to monitor the background flux from the ambient air and each probe in turn, at specified  intervals.

Scenario 4 hydrogen bakeout

Multiple sites are monitored continuously during a pre-weld hydrogen bake out at 3-4 locations to confirm that the bakeout is complete.

HT-R Battery recharging and USB

Battery charging and data retrieval is carried out in a hazard free area.


The instrument will be calibrated at factory. Equipment as previously supplied with Hydrosteel 6000 will be optionally provided for bump testing of flow and sensor response in an office environment,.


The instrument should require minimal maintenance, using just a damp cloth and mild detergent to clean up instrument surfaces.