With the static contact angle measurement, it is possible to
determine the hydrophobic properties of the NCIs surface.
The hydrophobicity is the degree of the water repellency
of the insulator surface. In this work, the sessile drop
technique was used for measuring the static contact angle
on the insulators, using the digital image analysis. A
precision pipette was used and the volume of each droplet
was 10 ml. For each sample ten droplets were put on the
top surface and the contact angle was measured.
Replication, a non-destructive technique, is generally used
to detect service failures in both ceramic and metallic
materials. It records and preserves the topography of a
micro-structural surface as a negative on a thin film of
cellulose acetate. In this technique, the film is first softened
using acetone and then applied to the surface. In the soft
state, the structure of the surface is replicated and preserved
when the film hardens after the solvent evaporates. In this
way, the technique is useful in preserving the microstructure
surface at various times during ageing [33].
Table 2 shows the main characteristics of the test chamber.
The UV radiation was simulated with 40 type UVA-340
fluorescent lamps and the UV irradiance at the insulation
apparatus is in the range of 0.65 W/m2. The design of the
salt-fog nozzles is as per IEC 601109, and the salinity of
the brine is 3 kg/m3