Materials testing

LMRC Material Testing and Development

 

 LMRC offers a range of laboratory-scale material tests. Testing is carried out in dedicated equipment that simulates the conditions that the materials are exposed to in an aluminium reduction cell but in an accelerated time-frame.

Cathode Materials Testing


   Inverted cell configuration for laboratory cathode testing

LMRC’s cathode testing facilities allows the electrochemical wear properties of cathode materials to be measured and compared. This testing allows cathode suppliers to determine the relative wear resistance of current or new materials and also lets smelters assess the performance on different blocks eg. When deciding to buy cathode blocks from a new supplier. 

The LMRC electrochemical wear test simulates the conditions the materials face in an industrial aluminium reduction cell. It exposes the cathode material to the corrosive electrolyte, fluoride gases and electrical current. The test uses an inverted cell configuration where the cathode samples are placed vertically down the centre of a graphite crucible that acts as the anode. This configuration promotes the electrochemical wear mechanisms and allows comparable wear rates to be achieved in a matter of days rather than years. 

LMRC works with a number of leading cathode suppliers on cathode related research,  and has also analysed samples on behalf of smelters looking to get a quantitative assessment of cathode performance. To learn more about this work see our TMS paper.
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Refractories Testing Procedure


  Schematic view of the refractory corrosion testing rig.

The lifetime of an aluminium reduction cell is an important factor in the operating economics of the smelter. Cell lifetime is increasingly driven by two components of the cell linings: the carbon cathode and the sidewall refractories. The sidewall materials are exposed to the reduction cell environment for years. Accelerated testing in lab scale experiments is required to simulate the conditions that lead to degradation of these materials in a shorter time frame.  Although samples tested in lab-scale configuration are small, they do inform the corrosion resistance ability of these materials, and the rig that is used in our lab exposes the sidewall materials to the various environments existing in a reduction cell: molten bath, CO/CO2 and corrosive gasses such as HF and NaAlF4. The corrosion tests results provide useful information regarding the quality of the sidewall material and can be used to compare corrosion resistance of different materials. To learn more about our corrosion test see our published paper.

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Bath Chemistry Characterisation


 Schematic view of DTA system and sample arrangement

Correct determination of cryolite ratio and superheat are important to keep the operation at optimal condition, and although established calculating methods exist for bath containing only cryolite, AlF3, and CaF2; it is more difficult to assess when other fluoride species are presented in the bath.

LMRC has developed a method using XRD and Rietveld/ Siroquant refinement to calculate accurate excess AlF3 (x AlF3) in bath containing other fluoride species such as LiF, MgF2 and KF. This enables accurate CR to be determined for smelters using bath with these fluoride components.

In addition LMRC has developed a DTA rig that can analyse liquidus point of bath samples and provide superheat information of different bath samples.

In order to understand more about our bath analysis you can read the paper LMRC published in TMS 2014 here.