Electrochemical behaviour of mild steel in some agro fluids

The corrosion behaviour of mild steel in some selected agro fluids such as apple, mango, grape, orange and the mixture of these agro fluids was electrochemically studied. A potentiometric analysis was employed to establish the comparative corrosion rates of this material in the agro fluids over the interval of five days for a sixty-day immersion period at a constant ambient temperature of 27±°C. The chemical composition of both mild steel and the agro fluids was determined to ascertain corrosion mechanism for the reaction. Polarization behaviours of mild steel in the agro fluids were determined by Tafel extrapolation curves. The analysis showed that cathodic polarisation curves were almost identical irrespective of variation in concentration of the various fluids while the anodic polarization curves exhibited varying active and passive corrosion behaviour due to passivating oxide films. The analysis of the results further showed that corrosion rates of the metallic alloy decreased with increase in immersion period which could be attributed to gradual decline in the concentration of the acidic level in these fluids within the given range of potential and scan rate. Hence, the evolution of hydrogen gas and reduction of oxygen molecules from the reacting system were presumed to be major factors retarding corrosion of the solution involved. Microscopic analysis of the corroded mild steel was revealed by SEM and EDS showed the respective compositions of the mild steel after the electrochemical tests. The result obtained from the study showed that electrochemical corrosion rate over the duration of immersion has greatest effect on the metal studied in orange medium (1.530 mm/yr), followed by grape medium (1.403 mm/yr), mango medium (1.339 mm/yr) while the metal in apple medium experienced the least effect (1.301 mm/yr). However, the mixture of these agro fluids showed more corrosive effect than the individual agro fluids with corrosion rate of 1.672 mm/yr.