Six-Year Evaluation of Thermo Sprayed Coating Zn/Al in Tropical Marine Environments

The main objective of this research was to evaluate the performance of thermosprayed coatings of zinc and aluminum (double layer) after 6 years of exposure, with and without the use of sealant (wash primer) in tropical marine environments of very high aggressiveness: La Voz (Cabo San Román / Falcón State) and Cruce del Lago de Maracaibo (Zulia State), in Venezuela. To that effect, carbon steel sheets (10 cm x 15 cm x 3 mm) were sprayed by flame. The sheets were characterized by means of initial weight, thickness, metallographic, adherence, roughness, being evaluated monthly by visual inspection and photographic during six years. After removal, the specimens were evaluated by microscopic analysis to determine the morphology of attack, microstructure, penetration of contaminants, composition and morphology of corrosion products. The results showed that after six years, the double layer system represents an excellent choice for corrosion protection of steel by combining the galvanic protection of zinc with the erosion resistance of aluminum. However, due to the erosion-corrosion effect, a sealant such as wash primer can be used in order to extend its service life.