Electrodes coating changed its color to purple, in the electrodialysis system (Micro ED, PCCell).

My solutions content as followed:

ER: Na2SO4 0.24 M

C: Na2SO4 3 g/L

D: Na2SO4 3 g/L + 200 ppm MgSO4.

My calibration storage solution for CEM/AEM has remained NaCl 3 g/L. During desalination, I have used AEM at both electrodes, and one cell pair. Before starting the experiments I had washed the system with C solution with 200 ml (C+D) circulation, and also washed electrodes with ER solution.

I wonder if high current for a long period of time can cause these changes, didn't notice color changes at the electrodes while working.

Electrodes material:

Anode: Pt/Ir- coated Titanium.

Cathode: V4A steel (chrome-nickel steel with molybdenum addition).

Hope you have ideas.

Rachel