What does chromate mean?
A chromate is a chemical salt or ester of chromic acid, characterised by the CrO₄²⁻ ion in which a chromium atom sits at the centre of four oxygen atoms in the +6 oxidation state. Chromates are typically vividly coloured — potassium chromate is bright yellow, and lead chromate was long used as the artist's pigment chrome yellow — a fitting property given that the element chromium itself takes its name from the Greek word for colour. Industrially, chromates have served as corrosion inhibitors, pigments, tanning agents, and oxidisers. However, their reputation has darkened considerably: hexavalent chromium compounds are highly toxic and carcinogenic, so uses such as zinc chromate primers have been heavily restricted or replaced. The term appears chiefly in chemistry, environmental regulation, and materials engineering, where phrases like 'lead chromate' and 'hexavalent chromate' are common.
nounA salt or ester of chromic acid, containing the anion CrO₄²⁻; typically a yellow crystalline compound of chromium in the +6 oxidation state.
- A salt of chromic acid containing the tetrahedral CrO₄²⁻ anion, in which chromium is in the +6 oxidation state.
- An ester of chromic acid, analogous to sulfate esters.
"The bright yellow pigment in old road markings was lead chromate."
"Potassium chromate solution turns from yellow to orange when acidified, forming the dichromate ion."
"Zinc chromate primer is prized for protecting aluminium aircraft skins against corrosion."
The plural usually refers to a class or family of different metal chromate salts rather than to countable individual substances.
"Soluble chromates such as those of sodium and potassium are strong oxidising agents."
Lead chromate gave the world its school-bus yellow — the same vivid pigment that made crocoite the first known chromium ore ever discovered.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of chromate
The word chromate comes from French chromate, coined around the turn of the 19th century after the discovery of the element chromium by Louis-Nicolas Vauquelin in 1797–98. Chromium itself derives from the Greek chrōma, meaning 'colour', chosen because chromium compounds display strikingly varied hues. The same Greek root gives English cognates such as chromosome, monochrome, and polychrome.
Related word forms
How chromate is actually used
Primarily a technical term used in chemistry, industrial coating, and materials science. Many chromates are toxic and carcinogenic because they contain hexavalent chromium, so the word often carries regulatory or safety connotations in industrial contexts. The plural 'chromates' refers to different metal salts collectively rather than multiple instances of one substance.
Easily confused with chromate
Chromite is a naturally occurring iron chromium oxide mineral (FeCr₂O₄) mined as the chief ore of chromium, whereas a chromate is a synthetic salt containing the CrO₄²⁻ ion.
A chromosome is a thread-like structure carrying DNA in living cells; despite the shared Greek root for colour, it has nothing to do with chromium chemistry.