George, The degree and rate of corrosion is strongly influenced by the difference between the two materials on the electro-galvanic chart. The rate of corrosion is also affected by the relative surface areas of the two materials. That having been said, it is my experience that pumps made from a combination of carbon steel and stainless steel exhibit long lives in many types of corrosive service. Many pump vendors will offer an "all iron" configuration with a 316 SS impeller. I do not believe you will have an acceleration of the corrosion rate that you now have with the inclusion of the SS pump. My experience only............ MJC