During air cooling from a high‐temperature anneal, vacancy currents were observed to cause zinc to segregate around vacancy precipitate cavities in aluminum. From the vacancy and zinc impurity currents directly measured in this experiment, a maximum value of the ratio of vacancy jump frequencies away from and around a zinc impurity atom in aluminum is determined. This limiting ratio suggests a small attractive interaction between a vacancy and a zinc impurity and/or an increase in the jump frequency of aluminum atoms around the undersized zinc atom. The segregation that would be produced around grain‐boundary vacancy sinks during quenching and irradiation was computed from the experimental values of the ratio of the vacancy current and the vacancy‐generated impurity current measured in this and other experiments. It was found that moderate and very large changes in grain‐boundary solute concentration could be expected during quenching and irradiation, respectively.