*2.3. Test Methods*

The corrosion behaviour of steel in mortar was evaluated by electrochemical measurement (EIS and anodic polarization curves) using a potentiostat/galvanostat Autolab PGSTAT 302N with Nova 2.1 software. A three-electrode system consisted of reinforcement steel (the working electrode), saturated calomel electrode (SCE; the reference electrode), and a stainless-steel plate (counter electrode) was used. Measurements were taken at a temperature of 20 ± 1 ◦C after 24 h of conditioning in a saturated solution of Ca(OH)2 in water.

The EIS measurements settings:


The equivalent circuit (Figure 2) for the analysis of the obtained EIS spectra was chosen under the assumptions described in a previous study [18]. The following parameters were determined on the basis of the measurements:


The EIS measurement was followed by an anodic polarization curve measurement. The settings for polarization measurements were as follows:


**Figure 2.** Equivalent circuit for steel in cement mortar (Re—the electrolyte resistance; Rm—mortar resistance; CPEm—constant phase element describing mortar; Rpas—the ohmic resistance in pits or defects of passive layer; CPEpas—the constant phase element for passive surface; Rct—the charge transfer resistance; CPEdl—constant phase element describing the double layer on the steel) [18].

The criteria for polarization data evaluation are given in [22] and [24].
