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The purpose of this paper is to investigate the effects of inorganic inhibitors on the corrosion rate of aluminum alloy using the electrochemical noise (EN) analysis and electrochemical impedance spectroscopy (EIS) techniques.

EN and EIS measurements were employed to study the corrosion behavior of aluminum alloy in Na₂SO₄(0.50 M)/NaCl(0.20 M) solution in presence of inorganic inhibitors. The time‐series noise patterns were transformed into the frequency domain using fast Fourier transformation, and then their power spectrum densities (PSDs) at specified frequencies were determined and compared with the EIS and polarization results.

The EN, EIS and polarization results were in agreement. The inhibitive effect of the anions decreased in the order: CrO₄²⁻>Cr₂O₇²⁻>NO₃⁻>WO₄²⁻>MoO₄²⁻>NO₂⁻. The results showed that the slope of PSD of the current (i.e. the “roll off”) was less where inhibition efficiency was greater. The spectral noise impedance and the modulus of the impedance recorded using impedance spectroscopy showed good agreement.

This paper provides useful information relative to corrosion inhibition efficiency of the sodium and potassium salts using EN analysis technique.