2003 Volume 52 Issue 8 Pages 401-407
The mechanism was studied of calcareous deposit growth on steel surfaces cathodically protected in seawater under a constant cathodic current density. The deposits grew in proportion to the electro-deposition time with keeping the Ca/Mg ratio almost constant. A SEM observation revealed that the deposit was composed of double layers with a clear boundary the inside of which was Mg-rich, and the outside Ca-rich. It was found from electrodeposition experiments added with the isotope of calcium, 45Ca, that the particles of CaCO3 and Mg(OH)2 were continuously moving in the deposits during the cathodic protection so as to build the boundary between the Mg(OH)2 and CaCO3 layers. The cause of this particles movement was attempted to explain from a colloid-chemical viewpoint.