Electro-chemical degradation (ECD) has been identified as a cause of failure in coolant hoses. Automotive industry trends towards higher under the hood temperatures and longer warranty periods are driving the introduction of more stringent technical specifications for ECD resistant products. Carbon blacks have been developed which modify the ECD resistance of hose compounds. This paper discusses the possible factors influencing electro-chemical degradation, an available test method for predicting ECD resistance, and carbon black's role in modifying an EPDM compound's ability to resist this phenomenon.