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Paint technoiogists shouid be very thankful to great scientist Sir Humphry Davy, and Michael Faraday for their valuable contribution in this field and their invention. In January 1824 almost 2 centuries back Sir Humphry Davy put forward his findings that iron and copper, and for that matter any other metal in sait water where oxygen is prevent, forms galvanic cells and one metal or the other is gradually dissolved, depending on the scale of intervention in the galvanic series. He proved that the traces of Zinc or even cheaper malleable iron could be placed in contact with water and thereby prevent corrosion.
Although being the bottom of the Ship, it is a priority to save this bottom from corrosion and fouling. Always being underwater it is a challenge to the paint formulator on devising methods to protect damage from pitting as propellors are made of brass and are in the vicinity, Zinc anode protects the paint only if the points are having alkali resistance. Earlier Coal tar epoxy was used having 350 microns DFT, but now days this has changed and pure epoxies are used as the coal tar has proved to be carcinogenic. Usually, Sealer coat is applied before antifouling to get smooth finish. |
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In the ocean of marine paints - V in PAINTINDIA, Vol. LXIV, N° 4 (04/2014)
