Stainless steel seed plates have become the default recommendation for durable backup storage. In practice, “stainless” does not mean impervious — and we see failures often enough to warrant a dedicated checkup item.
What Corrosion Looks Like
During a custody review last spring, a client brought a plate stored in a coastal Busan deposit box. Words stamped near the plate edges showed pitting — small dark spots where the surface had degraded. Words in the centre remained legible, but two characters near a mounting hole were ambiguous.
The client had chosen 316-grade steel, which resists salt air better than 304, but the deposit box environment still exceeded what the plate experienced during manufacturer testing.
Storage Conditions That Accelerate Damage
- Safety deposit boxes in basement levels with poor ventilation
- Plates stored inside ziplock bags that trap moisture
- Direct contact with rubber or foam padding that off-gasses
- Temperature cycling between unheated storage and heated living spaces
What We Check During Reviews
We photograph plate condition (never the words themselves — only edge areas and mounting points with your permission). We note the storage container type, last inspection date, and whether the stamping method (engraving vs punching) affects legibility.
If pitting is present, we recommend re-stamping or creating a fresh copy before the affected words become unreadable.
Practical Recommendation
Schedule a physical inspection of metal backups at least every two years, regardless of how “permanent” the material feels. Add this date to your custody log alongside your seed phrase verification date — they are related but distinct checks.