I agree with the observation of kendan, EPDM is suitable for caustic soda but not for oil that may be contained in the "spent caustic".
I recommend you use an o-ring of CR or FKM, both are suitable for both fluids.
Hi, I've a exudation problem on EPDM compound. it's very curious problem.
I use EPDM of hi-content of ethylene and paraphinic process oil. This row materials are used since 3 years w/o problems and now the oil exudes in both raw and volcanized state.
Several test was made in order to be sure of...