Potassium dichromate

Potassium dichromate, also known as potassium bichromate or dipotassium dichromate, is an inorganic chromium(VI) salt with the chemical formula K2Cr2O7. It is a strong oxidising agent supplied as a crystalline solid and is not assigned an E-code, as it has no approved food applications.

In leather tanning, potassium dichromate acts as an oxidising pre-treatment that converts sulfides and organic matter, improving chrome uptake during subsequent processing. In metal finishing and corrosion inhibition, it forms a protective chromate conversion layer on aluminium and zinc surfaces by reacting with the base metal to deposit a barrier oxide film.

Potassium dichromate is available in technical and laboratory reagent grades. As a Substance of Very High Concern (SVHC) under REACH, its supply and use within the EU requires authorisation for most applications. It is typically packaged in sealed polyethylene-lined drums or fibre kegs with full SDS documentation.