1 Litre Quickfit reaction vessel

Retort Stand with clamp

Auxiliary Electrode (Black lead) with 1cm2 Band of Platinum adapter and sealing plug. When inserting the Platinum Electrode into its adapter we recommend that the adapter is first dismantled so as not to damage the Platinum Band as it is inserted through the adapter. Typically the Auxiliary Electrode is used to supply current to the cell during a Polarisation.

Reference Electrode Storage Bottle

Reference Electrode Reservoir with cap seal tubing Hoffman clip and Pipette Filler.

In some cases it is deemed necessary to effectively isolate the reference electrode from the cell via a salt bridge. Typical reasons for this are: pollution caused by Reference Electrode extreme heat in the test cell and the desire to reduce solution resistance by placing the Luggin probe as close as possible to the test electrode. Although such experimental set ups look professional if possible they should be avoided as they can be the source of problems. Air leaks around the remote reference electrode are a typical problem causing a gradual dropping of the fluid level and eventual draining of the salt bridge. Typical location of air leaks: Cap Hoffman clip tubing joints. Bubbles in the Salt Bridge are also another typical problem. Indeed the typical result of the reference Electrode becoming isolated from the cell is that the test electrode is effectively dissolved by excessive polarisation. Another perhaps less well known effect is cause by the problem of Noise Induction. Noise induction is caused by the differential mains pick up at the cell and reference electrode. This effect is more noticeable when a typical commercial reference electrode is used and made worse with a salt bridge. Although usually ignored the level of this signal can be as much as 1 V. This signal feeds into the Potentiostat as if it is an external input which is then used to polarise the test specimen. For instance two identical tests placed on different positions on the same bench will be polarised by different levels of mains signal polarisation. The effect of this polarisation on the test results may be profound. The level of this polarisation can be reduced with the use of a Noise Reduction Probe as provided with the cell kit.

Luggin Probe with adapter and sealing plug.

Noise Reduction Probe (Blue) Platinum pin type tip adapter and sealing plug. The Noise Reduction probe is particularly useful at reducing mains signal polarisation caused by an imbalance of mains pick up in the Electrochemical Cell. Typically these electrodes should be used when a salt bridge is used or a typical commercial Reference Electrode. Further details can be found at our web site under Application Notes / Noise Induction.

Two Electrode Probe with adapter and two 7.5cm2 mild steel electrodes 3mm thread with sealing plug.

Gas Distribution Tube with sealing plug.

Exhaust valve

Polypropylene cell lid with clamp.

Cell lids are supplied pre drilled. The sping clamp is used to clamp the lid to the cell top. It may be necessary to slightly loosen the clamp. Blank cell lids can also be supplied.

Typical Cell Configurations

Fig 1: Simple three electrode set up using a metallic Reference Electrode. This type of cell may be adequate particularly when test types are performed over a short period of time such that any drift in the Reference Electrodes potential during the test is likely to be small. The set-up may also have benefits in situations where mains interference is a problem.

Fig 2: This cell arrangement is similar to figure 1 except that a typical commercial Reference Electrode (normally Saturated Calomel Electrode in ACM cell kits) is used instead of a metallic reference. In some cases it may be wise to use the Noise Reduction Probe to cut down mains signal polarisation of the test electrode. For further details please view our web site under Application Notes / Noise Induction.

ACM automated instruments have an internal ZRA this enables them to perform electrochemical tests on either an individual electrode (WE 1) or a Galvanic couple of Electrodes (WE1 and WE 2). In this later case provided the Weld test option is not selected then the couple of electrodes behaves as if it is a single electrode however current measurements are only taken from WE 1. In most cases operators will only use a single Electrode. It is important that if only a single electrode is used then this is connected to WE 1 and not WE 2.

Figure 3: This configuration is typically used for two electrode LPR type tests. In this configuration just the centre two electrode probe is used. The Auxiliary Electrode and Reference Electrode leads are connected to one of the leads whilst WE 1 is connected to the other lead. In this situation the polarisation current has to pass through two charge transfer layers. It is suggested that if the two electrodes are of the same material then an area of half the electrode area is used to compensate for this effect. If the common Auxiliary / Reference Electrode is either a lot bigger than or much more active than the test electrode then it may be reasonable to not alter the electrode area.

Figure 4: Typical Configuration of the cell for Current & Voltage Noise tests or for Galvanic and Potential monitoring. For improved Potential measurements or in situations where mains interference is a problem we recommend the use of the Noise Reduction Probe.

Figure 5: Customisation of the cell. The cell is provided with a range of plugs which can be used to block off unwanted holes in the cell lid. These blanking plugs can be drilled for customisation purposes. Alternatively the adapters can be used to mount your own 7mm diameter electrodes. Figure five shown a typical cell with a rotating disc electrode system.