Polarization Studies of Brass-Steel Galvanic Couples

Electrochemical polarization methods were utilized to study the galvanic corrosion of steel coupled to brass. Polarization of a 70Cu-30Zn brass cathode controlled galvanic corrosion rate (galvanic current) of the steel anode in the couple. The effect of cathode/anode surface area ratio was predicted successfully from a single pair of polarization curves on cathode and anode. Above 40% copper, copper-zinc alloys behave essentially like pure copper. Below this critical composition, the alloys behaved like pure zinc. Dichromate inhibitor decreased galvanic current by increasing cathodic polarization on 70 Cu-30Zn brass; nitrite did the same by increasing anodic polarization on the steel. Tolytriazole (TTA) increased polarization on both brass and steel, but the resultant decrease (inhibition) of the galvanic current was not as great as that of either dichromate or nitrite at the same concentration.