IMPEDANCE OF FE80B20 GLASSY ALLOY IN SULFURIC-ACID

Experimental investigations or corrosion behavior of glassy metal Fe80B20 in 1.0 mol dm-3 H2SO4 are described. Results are presented on voltametric and impedance measurements in three distinct anodic potential ranges. Two relaxation processes have been observed and identified: i) a kinetically controlled interracial charge transfer mediated by adsorption of some intermediate species in the active dissolution range; ii) the same process, but with a blocking effect due to adsorption of the passivating species in the passivation or transition range; and iii) ion migration in a high electric field within the passive layer with adsorption of surface states in the passive range. Using a general impedance of the resistance, the measured impedances have been characterized in terms of parameters of compatible equivalent circuits.