THE ELECTROCHEMICAL BEHAVIOR OF Zn– Mn ALLOY COATING IN CARBONATED CONCRETE SOLUTION

In order to improve the protective performance of zinc coating on reinforcing steel in concrete, this study investigates the electrochemical deposition of Zn–Mn coatings on steel surfaces. The first part evaluates the morphology, chemical, and phase compositions of the coatings obtained from a sulfate–citrate bath. In the second part, the deposits are subjected to tests in a solution that simulates carbonated concrete, composed of NaHCO3 and Na2CO3. Tafel analysis reveals that the Zn–Mn alloy deposits achieve higher corrosion resistance compared to pure zinc when deposited at –1700 and –1800 mV versus SCE. Impedance spectroscopy further indicates a steady increase in total impedance of the Zn–Mn coatings over time, significantly surpassing that of pure zinc after 24 hours in the corrosion solution. Conversely, the impedance for pure zinc rises within the first 12 hours before declining during extended exposure, attributed to the rapid development of non-protective white rust and degradation of the zinc coating, as confirmed by optical microscopy following 24 hours immersion in the carbonated concrete pore solution.