Hydroxide ions formed precipitate calcium carbonate on the surface of the electrode, forming a compact deposit.
The setup used in the Fig. 1 was developed by Ledion et al. (1985) [10] and used at the Ecole Nationale Superieure des
Arts et Métiers. It should be noted that the test conditions have been improved by Ledion (1994) [11] by following the
steps in order to have good sensitivity and good reproducibility with a fixed electrode and this, to overcome the
problems related to the use of a rotating electrode. The main operations are