Acid-induced corrosion mechanisms of galvanized and non-galvanized steels: Weight loss and EIS analysis with nanotechnology-enhanced surface engineering

Abstract

This study systematically evaluated the corrosion behavior and structural evolution of galvanized steel (GS) and low-carbon steel (LCS) in a citric acid medium (pH = 3) using gravimetric, electrochemical, and surface characterization techniques. Weight-loss measurements revealed that GS experienced a marked decrease in corrosion rate with increasing immersion time due to the formation of a protective zinc-based passive layer, whereas LCS showed a gradual increase in corrosion rate, indicating continuous surface degradation. Tafel polarization results confirmed this behavior, with GS exhibiting a more negative corrosion potential and lower effective corrosion activity as a result of enhanced passivation. XRD analysis identified stable ZnO/Zn(OH)₂ phases on GS, while LCS primarily formed iron oxide and hydroxide corrosion products. Optical microscopy demonstrated that GS maintained a dense and uniform surface morphology, whereas LCS suffered from pronounced pitting and surface coarsening. FTIR spectra further verified the formation of oxide and hydroxide species on both materials. Overall, galvanized steel showed superior corrosion resistance in acidic environments, highlighting the effectiveness of zinc coatings in protecting low-carbon steel substrates. Additionally, nanotechnology-based approaches such as nanostructured coatings and nanoscale surface modification can further enhance corrosion resistance by improving passive film stability, reducing porosity, and increasing surface uniformity in acidic environments.