**2.5 Laboratory tests**

After curing process, panels of 150 x 80 x 2 mm were immersed in 0.1 M sodium chloride solution for 90 days at 25 °C and pH 7.0. A *visual inspection* was realized throughout the experience; in addition, the *electrode potential* was determined as a function of exposure time; two clear acrylic cylindrical tubes were fixed on each plate (results were averaged).

The tube size was 10 cm long and 5 cm diameter, with the lower edge flattened; the geometric area of the cell was 20 cm2. A graphite rod axially placed into the tubes and a saturated calomel electrode (SCE) were selected respectively as auxiliary and reference electrodes. The potential was measured with a digital electrometer of high input impedance.

Similar panels were tested in salt spraying (fog) chamber (1500 hours) under the operating conditions specified in ASTM B 117. After finishing the tests, the panels were evaluated according to ASTM D 1654 (Method A, in X-cut and Method B, in the rest of the surface) to establish the *degree of rusting*.

Reinforcement Fibers in Zinc-Rich Nano Lithiun Silicate Anticorrosive Coatings 165

The electrode potential measurements as a function of immersion time indicates that both types of binders had a significant influence on the electrode potential: in general, more negative values were obtained with nano-structured film-forming materials, which means that the primers based on lithium silicate showed better cathodic protection than those

On the other hand, slight differences in electrode potential could also be attributed to the average diameter of zinc particles; it was observed greater galvanic activity in samples prepared with 4 μm than with 8 μm (values more negative of electrode potentials for the

> 0 10 20 30 40 50 60 70 80 **Immersion time, day**

> 0 10 20 30 40 50 60 70 80 **Immersion time, day**

Fig. 3. Electrode potential vs. immersion time in 0.1 M sodium chloride solution at pH 7.0 and 25 °C for primers based on 7.5/1.0 nanosilica/lithium oxide molar ratio, fine microzinc

manufactured with ethyl silicate.

**PVC, 57.5%**

A.I.2.c A.I.2.b A.I.2.a A.I.1

**PVC, 70.0 %**

A.I.2.c A.I.2.b A.I.2.a A.I.1

former than for the latter).



and graphite fibers.




**Electrode potencial, V/SC**

**E**







**Electrode potential, mV/SC**

**E**





Table 1. Primer identification.
