To obtain a galvanic anode suitable for preventing the corrosion of iron reinforcing bars in reinforced concrete by using an Al alloy contg. specified amts. of Zn and Sn and the balance Al with inevitable impurities.

The Al alloy contains 7-50 wt.% Zn and 0.01-0.60 wt.% Sn. Both Zn and Sn inhibit self-dissolution and act to increase the quantity of electricity generated. In the case of <7 wt.% Zn and <0.01 wt.% Sn, the action is not satisfactorily exhibited. In the case of >50 wt.% Zn and >0.60 wt.% Sn, anode potential is liable to become noble. When the Al alloy is used as a galvanic anode, such a sufficiently base anode potential as S-1,201 mV and such a sufficiently large quantity of electricity generated as ≥1,475 A.hr/kg are ensured and the corrosion of iron reinforcing bars in reinforced concrete is prevented.