Corrosion process ionic levels

As to the membrane conductivity, only small losses of protonic conductivity, of the order of 5-10% after 4000 h, have been observed in well-humidified cells during PEFC life tests according to measurements of cell impedance at 5 kHz [42]. The deionized water employed in the humidification scheme [42] had very low levels of metal ions (e.g., Fe " / +, Ca + or Mg +). Such multivalent ions could exchange irreversibly with protons in the PFSA membrane, causing a drop in membrane conductivity. Deionizing the water used for PEFC humidification is therefore required, and appropriate plumbing should also be used in the humidification loop to avoid generation of ionic contaminants by corrosion processes. 

The metal corrosion in soils is determined primarily by such factors as moisture content md its level of electrical (ionic) conductivity, aeration and oxygen content, relative acidity or alkalinity, and amount of dissolved salts. The two conditions necessary to initiate metal corrosion in soil are water (moisture) and oxygen. After these factors, a number of variables can affect the corrosion process. 

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