Rust Stains on Instruments – Why They Occur and What Helps

The instrument says “stainless” – and yet after a few months there are brown spots at the joint. Grounds for a complaint? Usually not. But an indication that something is going wrong in how it is handled.

“Stainless” does not mean “never rusts”

Stainless steel contains chromium. In air this chromium forms a wafer-thin, invisible passive layer – the actual protective layer. It repairs itself as long as it gets oxygen.

Rust arises where that layer is disturbed: under deposits, in damp gaps, on contact with chlorides. The steel is not bad then – it has merely been denied the chance to protect itself.

Extraneous rust or genuine corrosion?

Extraneous rust is foreign rust. Tiny iron particles – from the water, from rusting neighbouring instruments, from the cleaning machine – settle on the surface and rust there. The steel beneath is intact. Extraneous rust sits on top and can be removed.

Pitting is genuine corrosion. Small, often dark depressions that cannot be polished away. Here the steel itself is attacked. On the cutting edge that means the end of the instrument.

The test: if the spot disappears after careful polishing and the surface stays smooth, it was extraneous rust.

The most common causes

• Moisture in the joint. Number one. After rinsing, water stays in the joint, and no oxygen reaches it there.
• Chlorides. Table salt, sweat, some disinfectants and hard tap water attack the passive layer directly.
• Contact with rusting steel. A single carbon-steel instrument in the same tray is enough to cover all the others in extraneous rust.
• The dishwasher. Aggressive detergents plus salt – the worst combination for fine instruments.
• Residues. Cleaning agent that has not been rinsed off completely keeps working as it dries.
• Wet storage. A damp case, a closed box, a wash bag – all places without air exchange.

Removing extraneous rust

1. Clean the instrument and dry it completely.
2. Carefully polish out the spot with a soft cloth and a mild metal-care product.
3. Rinse thoroughly, dry immediately.
4. A tiny drop of instrument oil into the joint.

Do not use: steel wool, scouring cream, coarse abrasive paper or wire brushes. They scratch the surface open – and the next rust settles into every scratch mark. They make the problem bigger, not smaller.

Prevention is easier

• Dry after every use – the joint above all
• Let it dry open, do not put it away closed
• A drop of oil in the joint regularly
• No dishwasher
• Do not store together with carbon-steel instruments
• Keep it dry and airy, not permanently in a closed case

For practices

In reprocessing one more point is added: the final rinse with demineralised water and complete drying before sterilisation. Residual moisture in the autoclave is one of the most common causes of spotting on whole sets of instruments. Always observe the manufacturer's instructions on the approved procedures as well.

When an instrument belongs out of service

Visible depressions on the cutting edge, a rough action despite cleaning, rust that comes back after polishing – then the passive layer is permanently destroyed. With instruments used on people, that is not a question of appearance.

Conclusion

Brown spots are almost always extraneous rust and almost always self-inflicted. Drying and oiling solve the problem more reliably than any polish.

At nagelzange.de:

• Nail scissors in stainless steel
• Nail nippers
• Cuticle nippers and cuticle scissors

Read also: Having nail scissors sharpened – when it is worth it.

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