Corrosion of galvanized transmission line tower stubs just above the concrete chimney has occurred at several locations in Tamil nadu. Transmission line towers running close to coastal area are attacked by chlorides and sulphates and the towers in the vicinity of chemical, petro chemical, fertilizer and other industries are subjected to aggressive chemical attacks. Because of the extreme climate conditions prevailing in certain areas, transmission line tower stubs/coping/muffing concrete have been severely deteriorated and stub angle were corroded very much. During submergence of stub steel above concrete chimney for some period in rainy season, water acting as salt dissolved electrolyte, the corrosion process is aggravated particularly in the presence of chlorides and phosphates. The resultant produces of rust and complex compounds with chloride have a larger volume than the original material. This leads to the formation of local cracks and chipoff, which allows salt to penetrate further into the affected stub where the process of corrosion will be more and more accelerated.
A mechanism of pitting or crevice corrosion will initially occur in the presence of aggressive chloride ions. An important consequence of pitting is that the localized attack may be very service, which may lead to structural catastrophe. Application of Protective coating to steel angles and addition of admixtures to the concrete is one of the best method of controlling corrosion in steel angle.Effect of providing coatings on stub angle, addition of admixtures in stub concrete, corrosion inhibitors and barrier coatings on stub concrete against corrosion had been investigated in the laboratory under accelerated environmental condition. Individual and combined effect of coatings have been evaluated using half cell potentiometer test. The parameters involved for the deterioration of stub concrete and stub angle of transmission tower foundations had been discussed and concluded that three level coatings explained in the paper performs effectively in resisting corrosion of transmission tower stubs.
corrosion, Galvanized iron, coating
