How should I protect a carbon steel Shusui from rust?
Updated Feb 2026
Carbon steel requires more active maintenance than stainless alternatives because it lacks the chromium content that provides passive corrosion resistance. For the Black Shusui, apply a thin coat of choji oil or mineral oil to the blade surface every two to three months using a soft cloth or dedicated maintenance kit. After any handling, wipe down the blade promptly to remove skin oils, which are mildly acidic and can promote surface oxidation over time. Store the sword in its saya in a low-humidity environment, away from basements or coastal climates where moisture is elevated. A humidity control packet placed near the display case adds an extra layer of protection during summer months.