Corrosion Behavior of Zn-2.0Al-1.5Mg Coatings in Simulated Marine Atmosphere

As the service environment changes, the widely used galvanized coating faces challeng- s due to its overly thick coating and insufficient corrosion resistance. Zn-2.0Al-1.5Mg coatings have emerged as an alternative to conventional galvanizing because of their excellent corrosion resistance and are extensively used in buildings, home appliances, and automobiles in harsh environments. The ma-rine environment, known for its high corrosiveness, faces considerable material corrosion problems. High-ly resistant materials, such as Zn-2.0Al-1.5Mg coating, stainless steel, have found applications in the ma-rine environment. However, the development period of Zn-2.0Al-1.5Mg coating is short, and further re-search is required to determine its suitability for highly corrosive marine atmospheric environments. Con-sequently, the laboratory dry-wet alternating cycle corrosion test method, corrosion mass loss, SEM, XRD, EIS, and potentiodynamic polarization were used to investigate the corrosion behavior (e.g., corro-sion kinetics, corrosion product evolution, corrosion morphology, and electrochemical behavior) of Zn-2.0Al-1.5Mg coatings in a simulated marine atmosphere. Results show that the initial corrosion prod-uct is ZnO at 168 h, with Zn5(OH)8Cl2<middle dot>H2O appearing after 168 h of corrosion cycles (336, 504, 672, 840, and 1848 h). The emergence of ZnO at 168 h is attributed to the shortened dry-wet alternating cy-cle time, while that of Zn(OH)2<middle dot> 0.5H2O at 1848 h is attributed to the depletion of Mg or Al elements. The corrosion rate of Zn-2.0Al-1.5Mg coatings in the simulated marine atmosphere exhibited an M-shaped curve over time, closely related to the evolution of corrosion products. Between 0 and 840 h, the corrosion rate increased, except for a decrease between 336 and 504 h; this trend may be attributed to the disappearance of ZnO and an increase in the amount of Zn5(OH)8Cl2<middle dot>H2O. Combined with the electro-chemical results, it is speculated that the corrosion will accelerate with further exposure after 1848 h