Investigation of the Susceptibility of Brasses to Crevice Corrosion by Immersion and Electrochemical Methods

Susceptibility of the brasses containing 15, 30, 35 and 37 wt.% zinc to crevice corrosion was studied using cyclic potentiodynamic polarization and electrochemical impedance spectroscopy techniques and immersion tests in which a glass lens was designed for providing a crevice. NaCl aqueous solutions containing 2, 3.5 and 5% NaCl supplied media of different concentrations of chloride ions. The results showed Increasing of zinc content in the brasses decreased their susceptibility to crevice corrosion. Increasing of chloride ion concentration in the media from 2 to %3.5 caused decreasing of the susceptibility, however more increasing of chloride ion concentration from 3.5 to %5 caused severe attach in the brasses. Also, it was found that there is a boundary layer at a distance (d) far off the gap opening on each specimen in which the height of gap from the lens surface could be calculated and reported as a critical gap (y) for the alloy in the related chloride. Calculations showed that with increasing zinc content in the brasses alloys, y as the susceptibility criterion increased from 13.39-17.4 μm, considerably.