EFFECT OF OXYGEN AND OXIDIZERS ON THE ELECTROCHEMICAL-BEHAVIOR OF ALPHA-BRASS IN AQUEOUS-SOLUTIONS OF DIFFERENT PH

The electrochemical behaviour of alpha-brass (Cu:Zn approximate to 70: 30) in naturally aerated, oxygen saturated and oxygen free acidic, neu tral and basic solutions of constant pH has been investigated. The eff ect of oxygen and oxidizers on the corrosion behaviour of the alloy in the different solutions has been discussed. The effect of oxygen or o xidizers on the corrosion parameters of the alloy is dependent on the solution pH. The removal of oxygen or oxidizers from acidic solutions increases the corrosion resistance of the alloy. In these solutions, t he presence of oxygen or oxidizers enhances disproportionation reactio ns which lead to the breakdown of the passive film formed on the alloy surface. The preferential dissolution of zinc has been found to destr oy the passive film, especially in acidic solutions. X-ray photoelectr on spectroscopic investigations (XPS) of the alloy surface after long immersion time in solutions containing Cr2O72- ions have shown that ch romium is not incorporated in the barrier film. Scanning electron micr oscopy (SEM) does not show remarkable difference between the polished surface and the surface after immersion in the test solutions, In-acid ic solutions containing dichromate ions increased corrosion rates have been measured and clear corrosion patterns in the scanning electron m icrographs have been recorded.