Evaluación del efecto de tratamientos térmicos sobre la resistencia a la corrosión del recubrimiento Zn-10Al

Abstract

CONDITION FOR PUBLICATION OF PROJECT. This study evaluated the effect of post-process heat treatments on the mechanical and anticorrosive performance of a Zn–10Al coating deposited on steel. Heat treatments were applied at 250 °C and 350 °C for 15, 30, and 60 min to assess their influence on electrochemical stability and durability in a saline medium. Characterization included Open Circuit Potential (OCP), Linear Polarization Resistance (LPR), potentiodynamic polarization, Electrochemical Impedance Spectroscopy (EIS), Scanning electron microscopy (SEM-EDS), Vickers microhardness (25 gf), and salt spray exposure according to ASTM B117. The results showed that treatment D (350 °C, 15 min) exhibited the best electrochemical performance, with a polarization resistance of 1855.50 Ω·cm², a corrosion current density of 14.01 μA/cm², a corrosion rate of 0.227 mm/year, and an EIS-derived resistance of 687.20 Ω·cm², outperforming the as-received Zn–10Al coating G1 (1535.00 Ω·cm²; 16.94 μA/cm²; 0.275 mm/year) and the galvanized coating G2 (881.35 Ω·cm²; 29.50 μA/cm²; 0.442 mm/year). Nyquist and Bode plots supported these results, showing a larger impedance response and a more capacitive behavior for the 15 min treatments. At the microstructural level, growth of the intermetallic layer was also observed, increasing from 4.3 μm in G1 to 9.2 μm in treatment D. Although some treatments increased hardness, no direct correlation was found between higher hardness and improved corrosion resistance. Controlled short-duration heat treatments therefore optimized the protective performance of the coating without compromising its integrity. Keywords: ZnAl coating, heat treatment, lineal polarization resistence, electrochemical Impedance Spectroscopy.