Electrochemical Corrosion Kinetics across Dissimilar Conductor Interfaces
Electrochemical corrosion kinetics across dissimilar conductor interfaces accelerate through moisture condensation, demanding perimeter sealing and barrier plating.
Occluded Cell Corrosion
Meaning
Localized chemical degradation occurs within small, restricted areas where the environment becomes far more aggressive than the surrounding conditions. Occluded cell corrosion is often found in the narrow gaps between battery terminals and their connectors or under the edges of insulation tape. In these tight spaces, the lack of oxygen and the concentration of ions create a rapid pitting effect that can destroy metal components.
Damage Mechanism
Stagnant conditions inside a crevice allow for the buildup of acidic species that cannot be washed away. During the process of occluded cell corrosion, the metal at the bottom of the pit acts as an anode and dissolves into the electrolyte. This reaction is self sustaining because the geometry of the gap prevents the neutralizing of the local environment.
The concentrated chemistry inside the hole accelerates the rate of metal loss far beyond what would be seen on a flat, exposed surface in the same environment.
Material Vulnerability
Aluminum and stainless steel components used in battery packs are particularly susceptible to this form of attack if the surface passivity is broken. Designers must choose materials and coatings that resist occluded cell corrosion to ensure the long term integrity of the electrical joints. Using sealants or specialized lubricants can help keep the aggressive fluids out of the vulnerable gaps.
Reliability Impact
Failure of an important electrical connection can lead to a sudden increase in resistance and localized heating. If occluded cell corrosion goes unnoticed, it can eventually cause a terminal to break or a busbar to fail under load. Regular inspection of the joints in a pack is necessary to identify the early signs of this hidden damage before it leads to a system failure.