How are chromium chemicals used in leather tanning?

Chrome tanning is a primary method for converting raw animal hides into leather, utilizing approximately 25 percent of all produced chromium chemicals. The process works by displacing water from the spaces between protein fibers and cementing those fibers together.12

The tanning process typically employs basic chromic sulfates, which are derived from sodium dichromate. There are two main techniques:1

• Single-bath method: The most common approach, where hides are soaked in revolving drums containing increasingly concentrated solutions of chromium sulfate.2
• Double-bath method: Hides are first treated in a mild chromic acid solution, followed by a second bath where sodium thiosulfate and acid react to deposit basic chromium salts onto the skin fibers.2

While essential to the industry, it is important to note that industrial processes, including some applications in leather production, may involve hexavalent chromium, which is highly toxic and hazardous to human health. Ethical industrial practices must prioritize worker safety and environmental protection to mitigate the significant risks associated with exposure to such hazardous substances.3