H2 /T  Monitoring during the  

Degassing Process in Al Melt

  • Graphical Display of H2 and Temperature Changes
  • Easily See  when to Stop Bubbling
  • Easy Installation and Easy Operation
  • Long Life with Cheap Maintenance
  • Memory Storage

What is AlproH M?

AlproH M is a portable quick- measuring system for the determination of dissolved hydrogen content in molten aluminum alloys.

The system comprises of a Probe, an Analyzer (includes connecting line), and an optional Probe stand. The probe can use indefinitely until it breaks a part.

A patented PARK-RAPP probe, housed at the tip of the probe, provides an EMF output which depends purely on the hydrogen partial pressure (pH2) and temperature in the melt. The sensor is housed in a robust, impact-resistant probe constructed from special high temperature alloy and graphite, which ensures that the AlproH Palm is able to withstand the harsh environments in the Al foundry.

The sensor and temperature outputs are fed into the analyzer, which when combined with the alloy interaction parameters, gives the dissolved hydrogen concentration in units of ml/100g Al.

How it works

▲ AlproH Plam test

The technology is based on a novel solid electrochemical hydrogen sensor, so called Park-Rapp probe, which, at an elevated temperature, is able to measure hydrogen content with reference to oxygen in the air through the adoption of proton conductor/oxygen ion conductor hetero- junction electrolytes. The principle behind how it can be used to measure hydrogen concentration is described below:

An impervious section of Park-Rapp probe (yellow and grey tube) is coated with Pt electrodes on both faces. The inside of the sensor (reference electrode) is exposed to the oxygen-containing air and the other side (working electrode) is to the hydrogen gas in the melt. For this arrangement, the measured EMF of the sensor, E is expressed as

E = E0 + 9.921x10-5 T log[H2]

, i.e. it depends logarithmically on the hydrogen partial pressure at the working electrode immersed in the melt. Here Eo, and T are sensor constant, and absolute temperature, respectively.

The schematic diagram below shows how a voltage is generated across the solid hetero-junction electrolyte exposed to a given hydrogen partial pressure (pH2)

Thus the hydrogen concentration can be calculated from the measured EMF. To work out the dissolved hydrogen content in the melt, the relation between the gas partial pressure of hydrogen and its solubility for Al melt must be known. From Sievert’s law, the dissolved hydrogen content in Al melt for a given hydrogen partial pressure, S is expressed as

logS= 2.796-2760/T+1/2logPH2-logfH

where S has units of ml/100gAl and T, f are absolute temperature H and alloy interaction parameter, respectively


The sensor is a YSZ tube itself attached with an In doped calcium zirconate (proton conductor) which has a high thermal shock resistance. It is then brazed with KOVAR which is subsequently welded to a stainless steel tube to prevent from hydrogen gas leak. The WE (working electrode) is protected from Al melt by covering with porous graphite and Al seal is adopted to prevent from oxidation during the cooling period. The probe responds fast enough that it takes about 3-5 minutes to complete the measurement.

The probe has long life time. It can be used until it breaks. But we recommend to calibrate it once in a three months or 100 times use. If it is malfunctioning by some reasons, analyzer recognizes it immediately to give a error-notice to the user.

The probe(20cm long) is equipped with a handle (40cm long) which is then electrically connected to the analyzer. Thermocouple installed in the handle acts as a reference electrode as well as temperature sensing for the WE of the sensor.


Measuring Range0.05-0.99 ml/100gAl
Accuracy±0.05 ml/100gAl or ±15% (whichever is greater)
<0.01 ml/100gAl or ± 10% (whichever is greater)
Measuring Time<5 min
Max. depth of Immersion250mm
Sensor Operating Temp.

660-700 ℃

Size120x244x46 mm

Probe Stand

For the convenience and safety purposes, we recommend to use probe stand when the AlproH Palm-measurement is made by inserting the probe into the hot melt. It is made to grasp the probe firmly with grip which can move up-and-down by pull and push action. It also provides with a cooling pad which enables the temperature of the heated probe to drop rapidly after taking out the probe from the melt.

Because the probe stand is made of Al alloys, it is light in weight and easy to deploy.

Fast, Accurate, Easy to handle and Long Life

Due to the use of patented air reference electrochemical sensor along with special measuring algorithm, the probe gives a fast reading in <5 minutes and a solid firm structure can be possible to make it immune to any mechanical and physical problems.

The graph below shows the accuracy test results where the hydrogen concentration is measured by AlproH palm with flowing known concentration of reference hydrogen gas in the furnace. They are measured at three different conditions but they give almost the same result.