Mechanistic Investigation of the Corrosion Behavior of Organic Zn14Al1.4 Composite Coating Under Simulated Tropical Marine Atmospheric Conditions

The coupled factors of high temperature, high humidity, and high salinity in tropical marine atmospheres severely threaten the long-term service performance of power transmission and transformation infrastructure. This paper establishes an accelerated cyclic testing protocol (salt spray → drying → damp heat → drying) to evaluate performance and elucidate the dynamic corrosion failure mechanisms of the organic Zn14Al1.4 composite coating. By integrating multiphysical characterization techniques (SEM, EDS, XPS) with electrochemical analysis, this study for the first time elucidates the dynamic transformation of corrosion products: initially dominated by Zn(OH)2, progressing to complex passive phases such as Zn5(OH)8Cl2·H2O, Zn5(OH)6(CO3)2, and Zn6Al2(OH)16CO3 in the mid-term, and ultimately dominated by Fe-based products (FeO, Fe2O3, Fe3O4, FeOOH) that drive interfacial failure. And a four-stage corrosion evolution model was defined: incubation period, accelerated degradation phase, substrate nucleation stage, and catastrophic failure phase. The investigation reveals a shift in the coating/substrate interface failure mechanism from purely physical barrier effects to electrochemical synergy, providing a theoretical framework for the optimized design and service-life prediction of anticorrosive coatings for transmission and transformation equipment in tropical environments.