ELECTROCHEMICAL NOISE RESISTANCE AS A TOOL FOR CORROSION RATE PREDICTION

Current and potential fluctuations (electrochemical noise [EN]) betwee n two nominally identical carbon steel electrodes were recorded in a s olution of sodium phosphate (Na3PO4) at different concentrations. Afte r passivation was reached, pitting was induced by addition of chloride s. Data were collected with different sampling rates. Linear polarizat ion resistances (LPR) also were measured. Electrochemical signals were transposed in the frequency domains using the fast Fourier transform. Statistical parameters from the signals in the time and in the freque ncy domains were compared with corrosion rates (V-c) as measured by LP R. Noise resistance (R-n) also was calculated. From standard deviation (sigma) values of the current and potential noises, pitting attack wa s revealed at its onset. Good correlation between data from the differ ent techniques was found. R-n gave values proportional to the polariza tion resistance (R-p). The issue of how sampling rate can affect EN da ta collection also was addressed.