Nitric acid is currently the most widely used passivating solution to protect stainless steel from corrosion in industrial applications. But nitric acid is dangerous in multiple environmental, safety, and processes, due to its highly acidic nature and the toxic fumes, greenhouse gases and hazardous waste it generates. Citric acid is a promising replacement as it can be produced from natural sources, requires lower acid concentrations and doesn’t generate toxic fumes or hazardous waste.
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Source: Phys.org