We investigated the role of second phases in the stress corrosion cracking of a complex copper–aluminium alloy CuAl9Ni3Fe2. We conducted slow strain rate tensile tests in synthetic sea water. Cracking is mainly intergranular. The crack path is determined by the electrochemical interactions between the α matrix and the second phases. We observe the selective dissolution of the aluminium rich areas that are anodic with respect to the α matrix. Under cathodic polarisation, the detrimental effect on mechanical properties is enhanced. The number of cracks is reduced. Crack blunting by dissolution is impeded.