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Bresle Patches
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The Bresle method uses the difference of conductivity of salts in water, each salt having a characteristic conductivity-versus-concentration relationship. The correlation between concentration and conductivity can be found in “Handbook of Chemistry and Physics”. The relationship is useful if the dissolved salt is known. Sodium chloride, the main salt in sea water, causes a big increase in conductivity with increased concentration.
The patch is applied to the surface to be tested, and a specified volume of deionized water is injected under the patch. Any soluble salts present on the surface will dissolve in the water. The fluid is extracted and its conductivity measured.
The conductivity of the collected salt solution depends on the volume of water used and its initial conductivity, and the amount of salt in solution depends on the area of the patch. The calculation of the salt per area is based on increased conductivity but in the IMO PSPC method the salt is calculated as sodium chloride, in the ISO 8502-9 method it is calculated as a specific mixture of salts, but expressed as Sodium Chloride. |
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