Meaning
Electrochemical failure modes characterized by the localized loss of a protective oxide film on a metal surface lead to accelerated corrosion. Passivity breakdown occurs when the stable layer on an aluminum current collector or stainless steel casing is compromised by high potentials or aggressive chemical species. Once the film is breached, pitting corrosion can proceed rapidly, which might result in cell leakage or internal short circuits.
The threshold for this event is determined by the pitting potential of the material in a specific electrolyte environment.
Pitting Potential
Voltage limits define the safety window within which the protective oxide remains stable. Above the passivity breakdown voltage, the metal surface becomes vulnerable to the nucleated growth of pits. This value is a measurable property that guides the selection of materials for high-voltage battery systems.
Electrolyte Interaction
Chemical components in the liquid phase play a role in the stability of the passivation layer. Passivity breakdown is often triggered by the presence of fluoride ions or acidic decomposition products that dissolve the oxide film. This interaction is more pronounced at elevated temperatures where the reaction rates are higher.
The loss of the protective barrier allows the electrolyte to react directly with the underlying metal.
Material Durability
Alloy composition and surface finish determine the resistance of a component to this type of failure. Manufacturers select high-purity aluminum or specialized stainless steels to delay the onset of passivity breakdown. A smooth surface finish reduces the number of sites where a pit can initiate.
