|Budget Amount *help
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1996: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1995: ¥1,900,000 (Direct Cost: ¥1,900,000)
Platinum anode to flow cathodic protection current was set on the carbon steel coupon-50mm width and lm length with various hydrophile coatings. A determined voltage was applied between steel and anode, then cathodic current and electrode potential at artificial defect with diameter of 2mm were measured under conditions with various applied voltage, amount of deposited sea salt, relative humidity (RH), and hydrophile property of coating. It was confirmed that this cathodic protection method was effective under some conditions, because the electrode potential of artificial defect decreased with incrcasing applied voltage, amount of deposited sea salt and PH.And it is advantage of this cathodic protection method to be effective such conditions with higher corrosivity.
Distributions of current density and electrode potential were analyzed based on measured results by using 1-dimensional model with equivalent electric circuit. Current distribution and resistance's of insulation layr under the anode, water film on the coating, and polarization resistance were given as functions of PH.Thus it was possible to estimate electrode potential at defects, and it was known as follows ;
1)When coating condition is good and there exists only one defect, cathodic protection current reaches as far as 3-5m.
2)When there exist two defects, it is difficult to protect both of them, though the defect near the anode can be protected. Arrangement of Anodes should be considered in this case.
3)Because almost all voltage drop is applied to insulating layr under the anode, resistance of this layr should be decreased.