Hybrid finishing coatings applied on laminar zinc primers

GIUDICE CARLOS A.; CANOSA, G.; ALFIERI, PAULA V.

INDUSTRIAL & ENGINEERING CHEMICAL RESEARCH

AMER CHEMICAL SOC

Lugar: Washington; Año: 2013 vol. 52 p. 8223 - 8229

0888-5885

Hybrid finishing coatings were formulated with several film-forming materials and reinforcement fibers. In all cases, the same tri-pigmented epoxy-polyamide coating based on laminar zinc was used as primer. The results indicated that well-wetted fibers improved mechanical properties of finishing coating films, such as tensile strength, modulus of elasticity, hardness, adhesion and impact resistance; on the other hand, elongation decreased according with type and level of reinforcement fibers selected. In addition, finishing coatings with semi-conductive fibers displayed in salt spray (fog) apparatus, a high dissolution of metallic zinc of primer since these fibers would act as cathode in galvanic cells. According to IR spectrum analysis, chemical degradation was observed only in coatings with the binder susceptible to basic hydrolysis due to the action of hydroxyl ions formed on semi-conductive fibers. Furthermore, non-conductive fibers included in finishing coatings displayed no changes in any film-forming material (even when alkyd resin was used) and neither promoted excessive zinc dissolution of primer.