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Optical interferometry techniques was use for the first time to measure the surface
resistivity/conductivity of the pure aluminium (in seawater at room temperature),
UNS.No305 stainless steel (in seawater at room temperature), and pure copper (in tab
water at room temperature) without any physical contact. This was achieved by applying
an electrical potential across the alloys and measuring the current density flow across the
alloys, during the cyclic polarization test of the alloys in different solutions. In the mean
time, optical iterferometry techniques such as holographic interferometry was used in situ
to measure the orthogonal surface displacement of the alloys, as a result of the applied
electrical potential. In addition, a mathematical model was derived in order to correlate
the ratio of the electrical potential to the current density flow (electrical
potential/electronic Current flow=resistance) and to the surface (orthogonal)
displacement of the metallic samples. In other words, a proportionality constant (surface
resistivity or conductivity=1/ surface resistivity) between the measured electrical
resistance and the surface displacement (by the optical interferometry techniques) was
obtained. Consequently the surface resistivity (ρ) and conductivity (σ) of the pure
aluminium (in seawater at room temperature), UNS.No305 stainless steel (in seawater at
room temperature), and pure copper (in tab water at room temperature ) were obtained.
Also, electrical resistivity values (ρ) from other source were used for comparison sake
with the calculated values of this investigation. This study revealed that the measured
value of the resistivity for the pure aluminium (7.7x1010 Ohms-cm in seawater at room
temperature) is in a good agreement with the one found in literature for the Aluminium
Oxide ,85% Al2O3 (5X10 10 Ohms-cm in air at temperature 30C0). Unfortunately,
there is no measured values for the resistivity of cupric oxide (CuO), Cuprous Oxide
(Cu2O), or even the oxide of the UNS.No304 stainless steel in literature to compared
those values with the measured values in this study.
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