Online Hydrogen Analyzer for Liquid Aluminium

Controlling hydrogen solubility in liquid aluminium alloys is a critical requirement in the aluminium products industry. Excessive hydrogen content can lead to the formation of voids/cavities during solidification. Conversely, under certain conditions, a moderate hydrogen content may be necessary to overcome shrinkage porosity. Therefore, establishing and controlling the hydrogen content during casting is of paramount importance.

Measurement principle:
This technology is based on a novel ceramic material (CaZrO₃-In) that can conduct hydrogen ions at high temperatures. The probe arrangement during hydrogen concentration measurement in molten aluminium is shown below. At the tip of the probe is a porous diffusion barrier. Hydrogen dissolved in the molten metal leaves the solution and forms hydrogen gas in the measurement chamber, as shown. The measuring electrode of the hydrogen concentration unit contacts this gas. The voltage from the hydrogen concentration unit is measured and since the reference hydrogen concentration is known, the concentration of hydrogen gas in the measurement chamber can be calculated. To determine the hydrogen concentration in the molten metal, the solubility of hydrogen must be known. The solubility of hydrogen in pure aluminium depends on temperature. Therefore, the temperature of the molten metal must also be measured to calculate the dissolved hydrogen content. Hydrogen solubility also depends on the alloy composition of the molten metal. Therefore, the solubility coefficient within the analyzer is adjusted for appropriate compensation.

Electrochemical probe characteristics:
Plug and play, no assembly required. Easy to use, integrates with thermocouples.
Durable and resistant to chemical attack and shock.
Economical. Typically, it can be used for more than 100 measurements or 20 hours of cumulative use, whichever comes first.
Fast and efficient, millisecond response speed, stable hydrogen measurement in <2 minutes.
Versatile, can be used for point inspection and/or continuous monitoring. The probe can be mounted on the arm of the analyzer or on a separate custom fixture or even be handheld throughout the measurement.
Traceability, calibrated reference gas can be purified through the probe (in situ) to verify the probe's sensitivity, response time and accuracy.