97 Ford Taurus, overheating! Antifreeze is coming out the expansion tank a dingy orangish brown..?

Ocionally the car will act up right before or after it begins to over heat... The RPM's will go up while I loose power and struggle to get the car above 30-40 mph.... Fairly new radiator and I have NO airconditioning connected at all.... Checked my oil which seems fine not milky like antifreeze is getting in there... Thinking to start small, but single mom, limited funds! Any suggestions besides the obvious thermostat