A seal (48) between first and second relatively rotatable members (26,28). The seal comprises an abradable material on at least one of the relatively rotatable members (26,28). The abradable material comprises an open cell metallic foam (60) and polymeric films (64) closing the cells (62) of the metallic foam (60). The seal (48) is used between compressor rotor blades (26) and a stator casing (28) of a gas turbine engine (10). The seal (48) combines the sealing properties of a closed cell metallic foam with the abradability and manufacturing control of open cell metallic foam.