The dark reddish orange color is commonly known as “rust”. Rust gets its name from iron oxide, which forms a reddish-orange coating on iron or steel when it’s exposed to oxygen. So the dark reddish orange color is often associated with rusty metal. However, rust itself can range in color from red and orange to brown and even black depending on the type of iron oxide formed. So more specifically, the darker orange rust color is called red iron oxide or ferric oxide (Fe2O3).
When iron oxidizes in the presence of water or moisture, it forms reddish-orange hydrated ferric oxide, which gives rust its classic coloration. This is the most common form of rust. So in summary, the dark orange rust color that most people are familiar with is specifically called red or ferric oxide. It’s an oxidized form of iron that lends its iconic color to rusty metal.
The Science Behind Rust’s Color
On a molecular level, rust gets its red-orange color from the electronic transitions involved when iron oxidizes. Here’s a more detailed look at the science behind the formation and color of rust:
| Iron Oxidation State | Formula | Color |
|---|---|---|
| Ferrous oxide | FeO | Black |
| Ferric oxide | Fe2O3 | Red-orange |
| Ferrihydrite | Fe2O3·0.5H2O | Orange, brown |
| Magnetite | Fe3O4 | Black |
– Ferrous oxide (FeO) forms first when iron is exposed to oxygen. It has a black or gray color.
– As more oxygen is absorbed, it oxidizes into ferric oxide (Fe2O3) which has a red-orange color characteristic of rust.
– Hydrated ferric oxide (Fe2O3·nH2O) maintains the orange rust color but can appear brownish.
– Further oxidation eventually results in black magnetite (Fe3O4).
The red-orange color arises when Fe2+ ions in ferrous oxide are further oxidized to Fe3+ ions in ferric oxide. This involves electron transitions in the d orbitals of iron. Specifically, electronic transitions between the t2g and eg subsets of d orbitals in the Fe3+ ion absorb blue and violet light, causing an orange color from the remaining reflected light.
So in summary, the dark orange rust color comes from electron transitions in oxidized iron (Fe3+) that absorb short wavelength light, leaving longer orange/red wavelengths to be reflected and seen. This gives hydrated ferric oxide its iconic red-orange rust color.
Common Names for Rust Color
In addition to rust, here are some other common names used for the burnt orange rust color:
– Red oxide
– Iron oxide
– Ferric oxide
– Mars red
– Red iron oxide
– Indian red
– Falu red
– English red
– Venetian red
Many of these alternative names come from the pigments that were originally made from mineral forms of iron oxide. For example:
– Indian red came from naturally occurring red iron oxide deposits in India.
– Venetian red was an artificial ferric oxide pigment first produced in Venice.
– English red originated from iron-rich red ochre clay deposits in England.
So while rust is the most widely used term, names like red oxide, Mars red, or Venetian red all refer to the same reddish ferric iron oxide compound that gives rust its color.
Uses of Rust Color
While rusting is typically seen as corrosion on iron or steel, the reddish rust color has been useful for many applications:
– **Pigments** – Rust-colored ferric oxide pigments have been used since ancient times for dyes, paints, inks, cosmetics and more. Popular examples are Indian red, Venetian red, and Mars red artist’s pigments.
– **Jewelry** – Rust converters can stabilize iron rust into durable ferric oxide for use in jewelry making. Rust-colored iron oxide jewelry has an earthy, organic look.
– **Staining wood** – Solutions of iron oxide salts can be reacted with tannins in wood to create rustic-looking rust stained wood. It brings out the wood grain by darkening softer parts more than hardwood.
– **Rust converters** – Chemical rust converters contain tannic acid or phosphoric acid that convert iron corrosion into more stable ferric oxide. This stops rust growth while keeping the rusty appearance as a coating.
– **Textile dyes** – Red ferric oxide pigments were historically used to dye fabric and clothing with a burnt orange rust color. Moderate lightfastness allows the rust color to persist.
– **Cosmetics** – Iron oxides are FDA approved for use in cosmetics. Red iron oxide provides a natural reddish tone for products like eyeshadow, blush, lipstick, nail polish and more.
So while rusting causes damage on iron alloys, the resulting iron oxide’s color has proven very versatile for use in art, design, woodworking, and other applications that take advantage of its reddish-orange hue.
Matching Rust Color
If you’re looking to match the burnt orange rust color, there are a couple options:
**Buy iron oxide pigments**
– Red iron oxide powder can be purchased from art supply or chemical vendors.
– Mixing it into paints, epoxy resins, wood stains, etc. will reproduce the authentic rust color.
– Common forms are natural and synthetic versions of hematite (Fe2O3).
**Use rust-colored paints**
– Many paint brands offer premixed rust colored paints, often labeled as “rust”, “red oxide”, or “Mars red.”
– Hardware stores carry spray cans of rust colored paint for metallic finishes.
– Artist’s oil or acrylic paint ranges will have rust/red oxide colors like burnt sienna, mars red, or venetian red.
**Match Pantone colors**
– Pantone colors like Pantone 158, 170, 171, 173 approximate a reddish rust hue.
– These allow consistent color matching across different paints, inks, and fabrics.
– Rust effect spray paints are available matched to these Pantone rust colors.
So in summary, you can reproduce the signature rust color by getting iron oxide pigments, premixed rusty paints, or by matching rusty Pantone colors for projects where you want to simulate a realistic rusted metal effect.
Conclusion
The dark reddish orange color commonly seen on rusty iron is specifically called ferric oxide or red iron oxide. This form of iron oxide (Fe2O3) produces the classic burnt orange rust color due to electronic transitions in the oxidized Fe3+ ion that absorb short wavelengths of light. While rusting of iron alloys is undesirable, the resulting iron oxide has been useful for pigments, dyes, stains, paints, cosmetics and more that take advantage of its signature burnt orange hue. Rust color can be reproduced using synthetic iron oxide pigments, premixed rust colored paints, or by matching rusty Pantone colors. So ferric oxide is responsible for the familiar “rusty” reddish orange color and continues to be a versatile coloring agent.
