Cobalt Alloy
Cobalt Alloy
Quick look
- Hardness window: 59–62 HRC after proprietary heat treatments (Extramarise, etc.).
- Toughness: Cobalt stiffens the matrix; molybdenum/vanadium keep edges from chipping.
- Corrosion profile: Highly stainless; resists bleach and humidity with routine care.
- Weight/feel: Medium weight with crisp, controlled closure.
Why it matters
Cobalt-alloy stainless became the hallmark of premium Japanese shears in the 1980s. Adding cobalt refines carbides and raises red hardness, letting blades stay sharp longer under friction. Makers such as Mizutani pair cobalt with molybdenum and vanadium then run specialized heat cycles (Extramarise®) to deliver a glassy glide and long life.
Shear pairing & edge compatibility
- Convex all-rounders: Ideal for wet/dry precision when you need the edge to stay keen.
- Swivel or offset handles: Alloy’s stiffness keeps alignment steady even with articulated pivots.
Technique map
- Slide and point work where you want zero resistance.
- High-volume salons needing long edge intervals without moving to powder steels.
- Barbers tackling dense hair who still want a smooth convex feel.
Real-world stress tests
- Edge retention: Plan on 900–1,200 salon cuts (~5–7 weeks at 25 cuts/day). Mizutani reports 60–62 HRC capabilities after Extramarise processing, explaining the longevity.
- Impact/drop resilience: More rigid than 440C; protect the tips to avoid chipping.
- Weight & in-hand feel: Balanced, neutral weight that keeps closures silky.
Maintenance notes
Wipe and dry after chemical work, oil pivots weekly, and keep tension neutral. Book sharpening with a cobalt-experienced tech every 6 months to maintain the convex polish.
Industry snapshot
- Mizutani Black-Smith Twig/Pixy: Built from cobalt alloy with Extramarise treatment for boutique dry work.
Trade-offs
- “Cobalt alloy” isn’t standardized—quality varies by maker and heat treat.
- Higher cobalt raises cost; expect premium pricing and service requirements.
- Harder matrix chips if you twist or cut bobby pins.
Sources
Related: Steel Types • Edge Types • Scissor Maintenance