Citric Acid Passivation Process

Passivation, as a general term, is used for imparting metal with some sort of protective layer. The goal of passivation is to protect the metal from corrosion, and there are many ways to passivate metal. Citric acid passivation uses concentrated citric acid to passivate metals like stainless steel and titanium. The concentrated citric acid works to pull iron from the surface, then forms a protective layer on the outside of the part like a protective shell.

The citric acid passivation process is often confused with another finishing process called pickling, but they are not the same. The acid passivation process begins by creating a citric acid solution with citric acid and water, ensuring the liquid is uniform. A uniform solution is integral to an evenly passivated finish. The acid solution is then heated, and the parts to be passivated are added to the solution and fully submerged for an amount of time that’s decided by the desired finish.

We formulate our citric acid solution using concentrated citric acid and deionized water, ensuring the best quality and consistently excellent results. Before we begin the passivation process, we thoroughly clean each part, ensuring all surfaces passivate evenly. Once we have completed the citric acid passivation process, we complete a copper sulfate test which analyzes the effectiveness of the passivation against corrosive conditions.

The method of citric acid passivation is most commonly employed when parts require higher corrosion resistance. Parts of all sizes can benefit from the oxidation layer produced by citric acid passivation, but the material of the parts dictates how well the passivation will work. While stainless steel parts are the most commonly passivated using citric acid, other metals like titanium can benefit equally. Industries that use passivated parts vary from automotive and aerospace to medical, food and beverage processing, defense, and chemical and wastewater treatment, where corrosive environments are most common.