Manganese dioxide, a potential catalyst in many electrochemical reactions, was explored as an effective activator in Al + 5% Zn alloy sacrificial anodes. The catalytic influence of MnO2 on the anodes was micro-structurally and electrochemically characterized using different electrochemical techniques. The process of incorporation of MnO2 not only improved the grain size but also the galvanic performance of the anodes significantly. A galvanic performance as high as 80% was achieved by incorporating an optimum quantity (0.5%) of MnO2 in the anode matrix. High and steady active open circuit potential, very low polarization and substantial reduction in self corrosion were achieved during galvanic exposure tests. Effective activation of the anodes by MnO2 was also revealed by the results of electrochemical impedance analysis. The tolerance to biofouling on the anode surface was studied by quantifying the number of micro-organisms on the anode surface after immersing in natural sea water containing the micro-organisms.