If you are referring to rust in your coolant your radiator flow is probably restricted due to build up inside of it. Some radiator shops offer a service where they remove the radiator and clean it out, or you can replace it with an aftermarket one. Next step would be to address the engine and there are products that can be used to flush it out. I guess I got that backwards.... Before you have the radiator addressed flush the block..
Any auto store sells radiator flush. You pour it in the radiator and let it run for awhile. It'll tell you on the bottle how long. I usually take off the top radiator hose going to the radiator after the specified time and aim it away from you so you're not wet or burned. Leave the car running and take off the radiator cap slowly to release pressure then take it off. Put a garden hose in the radiator and. Turn it on and let the water circulate through the engine and out the top radiator hose. When it comes out clear clean water you're done flushing out the system. Replace the top hose, drain water back out through the petcock on the bottom of radiator. Winterize it with the right amount of antifreeze.