**3.3 Corrosion inhibitors**

The corrosion inhibitors tested in this study were natural honey, vanillin and tapioca starch. The choice of natural honey (NH), vanillin (VL) and tapioca starch (TS) as corrosion inhibitors for the study were based on the following:


The Nicolet 380 Fourier transform infrared (FTIR) spectrometer was used to determine the function group for each inhibitor.

#### **3.4 Electrochemical measurements**

All electrochemical measurements (PP, LPR and EIS) were accomplished with Autolab frequency response analyzer (FRA) and general purpose electrochemical system (GPES) for Windows-version 4.9.005 coupled to an Autolab potentiostat connected to a computer. The cell used consists of conventional three electrodes with a platinum wire counter electrode (CE), a working electrode (WE) and a saturated calomel electrode (SCE) as reference to which all potentials are referred.

The WE was in the form of a square cut so that the flat surface was the only surface in the electrode. The exposed area to the test solution was 3.75 cm2. The WE was first immersed in the test solution and after establishing a steady state open circuit potential, the electrochemical measurements were performed. The cell was exposed to air and the measurement was conducted at room temperature (25.0 ± 0.1 ºC). Triplicate experiments were performed in each case of the same conditions to test the validity and reproducibility of the measurements. All procedures for electrochemical measurements were performed in accordance with the Standard Practice for Calculation of Corrosion Rates and Related Information from Electrochemical measurements (ASTM G 102).
