Meaning
Electrochemical voltage limits define the point where the protective oxide layer on a metal surface breaks down in the presence of aggressive ions. The pitting potential marks the transition from general passivity to the formation of deep and localized holes. In battery cooling systems, this value determines the compatibility of the aluminum heat exchanger with the coolant chemistry.
Corrosion Resistance
Materials with a higher voltage threshold can withstand more aggressive environments without structural failure. When the operating voltage stays below the pitting potential, the metal remains protected by its thin surface film.
Electrolyte Chemistry
Chloride concentration and acidity significantly lower the voltage required to initiate a pit. Testing the pitting potential involves a potentiodynamic polarization scan that measures the current response as voltage is increased. A sudden spike in current indicates that the passive film has been breached and active dissolution is occurring.
This test is vital for evaluating the longevity of current collectors in high voltage battery chemistries. Understanding the relationship between salt concentration and film stability prevents premature leakage of the battery cell.
Passive Film
Regeneration of the oxide layer must occur faster than the dissolution rate to maintain the surface. Below the pitting potential, the metal naturally heals itself through the reaction with oxygen or water.
