Rust Stains on Instruments – Why They Occur and What Helps

The instrument is marked “stainless” – and still, after a few months, there are brown spots at the joint. Grounds for a complaint? Usually not. But a sign that something is going wrong in day-to-day handling.

“Stainless” does not mean “never rusts”

Stainless steel contains chromium. In contact with air, this chromium forms an extremely thin, invisible passive layer – the actual protective film. It repairs itself as long as it gets oxygen.

Rust forms wherever this layer is disturbed: under deposits, in damp gaps, on contact with chlorides. The steel is not poor quality – it was simply denied the chance to protect itself.

Surface rust or real corrosion?

Surface rust is foreign rust. Tiny iron particles – from the water, from rusting instruments lying next to it, from the cleaning unit – settle on the surface and rust there. The steel underneath is intact. Surface rust sits on top and can be removed.

Pitting is real corrosion. Small, often dark pits 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 surface rust.

The most common causes

• Moisture in the joint. Number one. After rinsing, water stays behind in the joint, where no oxygen reaches it.
• 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 surface rust.
• Dishwasher. Aggressive detergents plus salt – the worst possible combination for fine instruments.
• Residues. Cleaning agent that was not rinsed off completely keeps working as the instrument dries.
• Damp storage. A wet case, a closed box, a wash bag – all places without air exchange.

Removing surface rust

1. Clean the instrument and dry it completely.
2. Carefully polish out the spot with a soft cloth and a mild metal polish.
3. Rinse thoroughly, dry immediately.
4. One tiny drop of instrument oil in 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 in every scratch. They make the problem bigger, not smaller.

Prevention is easier

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

For practices

In reprocessing, one more point applies: the final rinse with demineralised water and complete drying before sterilisation. Residual moisture in the autoclave is one of the most common causes of staining on entire instrument sets. Always follow the manufacturer's instructions on the approved procedures as well.

When an instrument should be taken out of service

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

Conclusion

Brown spots are almost always surface rust, and almost always home-made. 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.