Citric Acid Passivation Process

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Citric acid passivation is a proven method for improving the corrosion resistance of stainless steel. By removing free iron and other surface contaminants, this process promotes the natural formation of a protective chromium oxide layer. Unlike nitric acid passivation, citric acid is a biodegradable, non-toxic alternative that delivers comparable results without the environmental and health hazards.

The Citric Acid Passivation Process
Step 1: Pre-Cleaning: Prior to the passivation process, stainless steel parts are subjected to an extensive pre-cleaning cycle to remove oils, grease, and metallic residues. The degreasing and cleaning of stainless-steel parts can be accomplished by a variety of commonly accepted methods, including acid pickle and an alkaline soak followed by a water rinse.

Step 2: Citric Acid Immersion: Once cleaned, parts are submerged in a citric acid solution—typically at a concentration between 4–10% and a temperature range of 70–140°F (20–60°C). The immersion time can vary between 20–60 minutes, depending on the temperature and specific material.

Step 3: Rinsing & Drying: After immersion, parts are rinsed with clean water to remove all residual acid and then dried completely. Proper drying is essential to prevent water spots and ensure that the passivation layer develops uniformly.

Step 4: Quality Testing & Inspection: Sample parts are tested to ensure they meet customer qualifications before being packaged for shipping.