---
title: "Does tungsten carbide rust?"
description: "tungsten carbide: it corrodes, but it does not rust. What actually happens to it over time, and why rust and corrosion are not the same thing."
url: https://atoneplace.net/does-it-rust/tungsten-carbide/
site: "At One Place"
---

# Does tungsten carbide rust?

**Does tungsten carbide rust?: It corrodes, but it does not rust**

tungsten carbide

The carbide is inert; the cobalt binder can corrode, which is why carbide tools pit in coolant over time.

## Rust is not the same as corrosion

Rust means iron oxide specifically. Only iron and things containing iron can rust, so "does aluminium rust" is a category error — aluminium corrodes vigorously and does not rust. That distinction is not pedantry, because the two oxides behave in opposite ways. Iron oxide is porous, flakes off and exposes fresh metal underneath, so rusting continues until the metal is gone. Aluminium, chromium, zinc and titanium form dense oxide films that seal the surface and stop the reaction, and re-form within milliseconds if scratched.

## What rusting needs

- Iron, oxygen and water — all three. Iron in dry air does not rust, and iron in oxygen-free water does not either, which is why iron shipwrecks in deep anoxic water survive and ones in shallow oxygenated water do not.
- Salt accelerates it dramatically, by making the water conductive and allowing the electrochemistry to proceed faster. This is the entire reason coastal and road-salted cars rot.
- Contact with a more noble metal accelerates it — galvanic corrosion. Steel bolted to copper or carbon fibre corrodes far faster than steel alone.
- Rust occupies roughly six times the volume of the steel it came from, which is why it cracks concrete and jams bolts rather than simply thinning them.

## How it compares

| Material | Rusts? | What actually happens |
| --- | --- | --- |
| mild steel | Yes — it contains iron, so it rusts | Rusts readily and completely. Unprotected mild steel outdoors loses measurable thickness every year. |
| aluminum | It corrodes, but it does not rust | Aluminium oxidises within milliseconds of exposure, and the oxide layer is dense, adherent and self-healing — the opposite of rust. This is why an untreated aluminium window frame outlasts a painted steel one. |
| water | Neither rusts nor meaningfully corrodes | Water does not rust; it is the agent that makes iron rust, together with oxygen. Neither alone is enough. |
| copper | It corrodes, but it does not rust | Copper forms a green patina of copper carbonate, which is protective and self-limiting. The Statue of Liberty is copper and its skin is about 2.4 mm thick after 140 years. |
| gold | Neither rusts nor meaningfully corrodes | Gold does not oxidise in air at any temperature. Gold recovered from shipwrecks after centuries is unchanged. |
| titanium | It corrodes, but it does not rust | Forms an extremely stable oxide film. Titanium is essentially immune to seawater, which is why it is used for submarine and marine hardware. |
| concrete | It corrodes, but it does not rust | Concrete itself does not rust; the steel inside it does, and that is the main way reinforced concrete fails. Rust occupies about six times the volume of the steel it came from, so it cracks the concrete outward from within — the stains and spalling on an old car park are that process. |
| stainless steel 304 | It corrodes, but it does not rust | Does not rust in normal use, because chromium oxide blocks it. It will stain and pit if the oxide layer is damaged and cannot re-form — under a rubber mat, or where iron particles from a grinder have embedded in the surface. |
| iron | Yes — it contains iron, so it rusts | Iron oxide is flaky and porous rather than protective, so rust does not stop the reaction — it exposes fresh metal and the corrosion continues inward until nothing is left. |
| air | Neither rusts nor meaningfully corrodes | Air does not corrode; it is half the reason other things do. Iron needs both oxygen and water to rust, and neither alone will do it. |
| ice | Neither rusts nor meaningfully corrodes | Does not corrode. It causes enormous mechanical damage by expanding about 9 % on freezing. |
| lead | It corrodes, but it does not rust | Forms a dull grey oxide-carbonate layer that protects it well. Lead roofing on cathedrals has lasted centuries. |
| tungsten | It corrodes, but it does not rust | Very resistant at room temperature; oxidises readily when hot, which is why filament bulbs had to be evacuated or gas-filled. |
| brass | It corrodes, but it does not rust | Tarnishes and can dezincify — in the wrong water chemistry the zinc leaches out and leaves a porous copper skeleton that looks intact and has almost no strength. Plumbing brasses are specified as dezincification-resistant for that reason. |
| pine | Neither rusts nor meaningfully corrodes | Does not corrode. It rots, which is a biological process rather than a chemical one and needs moisture and oxygen. |
| silver | It corrodes, but it does not rust | Silver tarnishes to silver sulfide, reacting with traces of sulfur in air rather than with oxygen — which is why it blackens faster near eggs, onions and rubber bands. |
| gray cast iron | Yes — it contains iron, so it rusts | Rusts fast when bare. Seasoning a pan is a polymerised oil layer that physically excludes water — it is a barrier, not a chemical passivation like stainless. |
| diamond | Neither rusts nor meaningfully corrodes | Chemically inert at room temperature. It burns in oxygen above about 800 °C. |

## Common questions

### Does tungsten carbide rust?

It corrodes, but it does not rust. The carbide is inert; the cobalt binder can corrode, which is why carbide tools pit in coolant over time.

### What is the difference between rust and corrosion?

Rust is iron oxide specifically, so only iron and iron alloys rust. Corrosion is the general term. The practical difference is that iron oxide is porous and lets the reaction continue, while aluminium, chromium, zinc and titanium form dense self-healing oxide films that stop it.

### Why does salt make things rust faster?

It makes the water conductive, which lets the electrochemical reaction proceed much faster. It is why coastal and road-salted vehicles corrode in a fraction of the time.

## Related pages

- [tungsten carbide](https://atoneplace.net/material/tungsten-carbide/)
- [Is tungsten carbide magnetic?](https://atoneplace.net/is-it-magnetic/tungsten-carbide/)
- [Does tungsten carbide conduct?](https://atoneplace.net/does-it-conduct/tungsten-carbide/)
- [Does aluminum rust?](https://atoneplace.net/does-it-rust/aluminum/)
- [Does copper rust?](https://atoneplace.net/does-it-rust/copper/)
- [Does titanium rust?](https://atoneplace.net/does-it-rust/titanium/)
- [Does concrete rust?](https://atoneplace.net/does-it-rust/concrete/)
- [Does stainless steel 304 rust?](https://atoneplace.net/does-it-rust/stainless-304/)
- [Does lead rust?](https://atoneplace.net/does-it-rust/lead/)
- [Does tungsten rust?](https://atoneplace.net/does-it-rust/tungsten/)
- [Does brass rust?](https://atoneplace.net/does-it-rust/brass/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)