DETERMINATION OF THE REACTIVE AREA OF ORGANIC COATED METALS - PHYSICAL MEANING AND LIMITS OF THE BREAK-POINT METHOD

The physical meaning of the reactive area values of a metal under an o rganic coating, obtained using the break-point method is discussed. So me experimental evidence is found which allows us to consider the area as related to coating defects and porosity, rather than to the total reactive or delaminated area. The limits for applying the break-point method are also obtained by mathematical considerations, showing that such a method is not correct when the values oi the coating capacitanc e and double layer capacitance are too close to each other. This possi bility is quite frequent during the initial time of degradation and al so when two time constants are distinguishable in the plot, as shown i n the presented experimental results.