Corrosion Fatigue Influence on Gasket Flange Cracking

This paper discusses corrosion fatigue and the corrosive environment as they relate to an industrial engine head gasket joint. The paper will identify possible corrosive elements which initiate corrosion fatigue failures. The sources of the corrosive elements will be cited with the associated concentration levels. The paper will formulate a hypothesis as to how the corrosive elements are transferred through the engine coolant system. Utilizing a Scanning Electron Microscope (SEM) and an Energy Dispersive X-ray Spectroscope (EDX), an analysis of coolant residue at the fracture will show evidence of the corrosive elements to verify the proposed hypothesis. Information from engines in the field will be compared to laboratory engine tests to show how laboratory and field results are significantly different. The main corrosive failure of the engine head gasket is flange cracking. Since this failure is truly a corrosion fatigue problem, one needs to know the stress history of the flange as the engine head gasket is manufactured and tested. With the knowledge of the corrosive elements and the stress levels, one can develop laboratory bench tests to evaluate the corrosion fatigue problem. Based on the above information, a simple MTS laboratory test has been utilized to evaluate the flange cracking problem. The ability to reproduce the corrosion fatigue problem will be explained and the MTS laboratory tests and the actual field failures will be compared. Finally, using the MTS laboratory corrosion fatigue test, several flange materials are compared.