Sweep off the concrete with a broom to remove dirt from the surface. You can enhance this step by using a pressure washer, but this is a more expensive and less practical option.
Put on rubber or latex gloves and safety goggles. Mix the concrete rust remover in a bucket of water using the specifications on the label. This is a powerful chemical, and even the most considerate safety measures cannot account for incidental splashing that can cause damage to your skin and eyes.
Saturate a rag in the rust remover mixture, and drape the saturated rag over the stain.Keep the rag on the stain for 10 minutes. Remove the rag, and use a stiff wire brush to scrub the stains out of the concrete. Rinse the rust remover off the cement thoroughly. The stain will lighten with each application and scrubbing, so repeat this process as necessary.