**3.1 Visual observation**

Immersion test in 0.1 M sodium chloride solution allowed to observe, particularly in those panels with X-cut, that coatings based on nano-structured film-forming material as binder showed greater amount of white products from corrosion of metallic zinc than in those panels protected with primers made with partially hydrolyzed ethyl silicate as binder. This performance would be supported in the less zinc dispersion ability that displays the first binder, which would generate films more porous.

On the other hand, primers that included fine zinc particles (4 µm) also showed a galvanic activity more important than those made from regular zinc particles (8 µm). A similar conclusion was reached with the primers based on microzinc/conducting reinforcement fibers (graphite and silicon nitride) with respect to those based just on spherical microzinc dusts and mixture with insulating reinforcement fiber (quartz). In turn, it was also observed a rise of the galvanic activity of metallic zinc when the amount of conducting fibers was increasing in the film.

For the lower values of PVC studied, the incorporation of conductive reinforcing fibers in increasing levels led to primers with a galvanic activity also increasing (similar amount of white salts than in primers formulated with PVC nearest to CPVC).
