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What is Corrosion Resistance?

Corrosion resistance is the ability of steel to resist rust, pitting, and chemical attack from its environment. Stainless steel needs at least 10.5% chromium, and the chromium dissolved in the matrix is what protects it. VG-10 has 15% total chromium and about 11.7% in solution per Knife Steel Nerds Thermo-Calc modeling, still above the 10.5% minimum. Salon chemicals including peroxide, ammonia, and chlorine test this property daily.

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What is Corrosion Resistance?

Why It Matters for Scissors

Professional hair scissors operate in one of the most chemically aggressive environments for cutlery. Stylists handle scissors with wet hands, expose blades to hair saturated with hydrogen peroxide (bleach), ammonia-based color, and chlorinated rinse water. A single day in a busy color salon subjects scissors to more chemical exposure than a kitchen knife sees in months.

Corrosion degrades scissors in two ways. General surface rust is cosmetic initially but creates friction that ruins the smooth blade action stylists depend on. Pitting corrosion is worse — it creates microscopic holes along the cutting edge that act like serrations, producing a rough, tearing cut rather than a clean slice.

More chromium in solution, and added molybdenum or nitrogen, all help. On paper 440C (16 to 18% Cr) has more chromium than VG-10 (about 15%, with about 11.7% in solution per Knife Steel Nerds modeling), while VG-10 adds about 1% molybdenum. Treat both the same in the salon: wipe and dry after every chemical service.

Technical Detail
Corrosion resistance in stainless steel depends on the formation of a passive chromium oxide (Cr2O3) layer on the surface. This invisible film, only a few nanometers thick, self-heals when scratched and prevents oxygen and moisture from reaching the underlying steel. The standard minimum for stainless steel is 10.5% chromium (EN 10088-1, ISO 15510). The critical distinction is between **total chromium** and **chromium in solution**. When steel is heat-treated, some chromium combines with carbon to form chromium carbides (Cr7C3 and Cr23C6). This chromium is "locked up" in the carbides and does not contribute to the passive layer. Higher-carbon steels lose more chromium to carbides. For VG-10 (about 1.0% C and 15% Cr, per Takefu), Knife Steel Nerds' Thermo-Calc modeling shows approximately 11.7% Cr remains in solution after standard heat treatment. This is above the stainless threshold but leaves less margin than lower-carbon alternatives. **Sensitization** is a related concern. If steel is held too long in the 450-850C temperature range during heat treatment, chromium carbides precipitate preferentially at grain boundaries, creating chromium-depleted zones that corrode first. This manifests as intergranular corrosion — corrosion that follows grain boundaries and can cause blade failure. Proper heat treatment avoids this temperature range or passes through it quickly. Environmental factors affecting salon corrosion: - **Hydrogen peroxide** (developer): Strongly oxidizing, attacks the passive layer directly - **Ammonia** (hair color): Alkaline environment accelerates pitting in chloride-containing solutions - **Sodium hypochlorite** (Barbicide, sanitizers): Chloride ions penetrate the passive layer and initiate pitting - **Sweat and skin oils**: Contain salts (NaCl) that promote crevice corrosion in the pivot area The PREN (Pitting Resistance Equivalent Number) formula provides a comparative metric: PREN = %Cr + 3.3 x %Mo + 16 x %N. Molybdenum and nitrogen both boost pitting resistance significantly, which is why nitrogen-alloyed steels like Sandvik 14C28N perform well despite moderate chromium levels.

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Best shears for color-treated hair →

References

Sources

2 sources
  1. Knife Steel Nerds (Dr. Larrin Thomas) (independent testing)
  2. Proterial / Yasugi Specialty Steel (旧日立金属・安来鋼) (manufacturer official)

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Quick clarifications

Frequently Asked Questions

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Why do some stainless steel scissors still rust?

If too much chromium is locked in carbides during heat treatment, the chromium in solution can drop too low to keep the protective oxide layer stable. Poor post-quench tempering or inadequate passivation can also cause localized corrosion.

Which scissor steels have the best corrosion resistance?

All the common scissor steels are stainless. On paper 440C (16 to 18% Cr) has more chromium than VG-10 (about 15% Cr, with about 11.7% left in solution per Knife Steel Nerds modeling), while VG-10 adds about 1% molybdenum, which helps against pitting. Nitrogen-alloyed steels like 14C28N also do well because nitrogen boosts pitting resistance. Whatever the steel, wipe and dry it after chemical work.

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Last updated: September 25, 2026 · by
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