The direct answer to whether tungsten carbide rusts is no. Rust is the specific oxidation of iron, forming hydrated iron(III) oxide. Since tungsten carbide is a composite material made of tungsten and carbon, it lacks the iron necessary for this reaction. This compound offers exceptional chemical stability, making it resistant to tarnishing and corrosion.
Why Tungsten Carbide Resists Rusting
The tungsten carbide (WC) phase is highly stable and chemically inert, meaning it does not readily react with many corrosive substances, including most acids and bases. This compound is formed from tungsten and carbon atoms, creating a ceramic-like structure. The inherent stability of this crystalline structure prevents the general oxidation and chemical breakdown common in many pure metals.
Rusting involves iron reacting with oxygen and water to create a flaky, reddish-brown substance. Tungsten carbide does not contain the necessary iron component for this electrochemical process to occur. Although the material can still be subject to other forms of chemical degradation, the tungsten-carbon compound maintains integrity across environments. This resistance to chemical attack is why the material is used in demanding applications, from industrial cutting tools to everyday jewelry.
The Critical Role of the Metallic Binder
Tungsten carbide products, also known as cemented carbides, are composites where the hard carbide grains are held together by a metallic binder. This binder, most commonly cobalt or sometimes nickel, provides the otherwise brittle material with necessary toughness and structural integrity. While the carbide itself is stable, the metallic binder is the material’s vulnerable point, and its degradation is often mistaken for rust.
This binder can corrode, particularly when exposed to strong acids, alkaline solutions, or high humidity and heat. This process, sometimes called “binder leaching” or “pitting,” involves the binder metal reacting with the environment and dissolving away. Cobalt-bonded tungsten carbide is more susceptible to attack in acidic or chloride-rich environments. Nickel-bonded grades offer improved corrosion resistance and are preferred for use in chemically aggressive or marine environments.
Caring for Tungsten Carbide Products
Proper care for tungsten carbide products centers on protecting the metallic binder from corrosive chemicals and preventing damage. Cleaning should be done with mild soap and warm water, using a soft cloth to remove any buildup of dirt or residue. It is particularly important to thoroughly dry the item afterward to prevent water spots, especially in crevices.
A primary precaution is to avoid exposing the product to harsh cleaning agents, such as bleach, ammonia, or chlorine, as these chemicals can attack and degrade the metallic binder. Although tungsten carbide is extremely scratch-resistant, the material is also brittle, meaning it can shatter under severe impact or thermal shock. Storing products in a soft pouch or original box when not in use helps protect them from accidental knocks.