I agree with Allen
The first you should do, is to run oil analysis of your EHC fluid. You have to know what is TAN, water content, particle count, Cl contents,conductivity, and metals content like Ca, Al, Mg.
Depending the results of the analysis, you should check the actions. Maybe, you will need to change the fluid, and performing a flushing of the system, or maybe, you could use ion exchange technology for controlling the problem.
Regards