Why is citric acid used for passivation?
Citric acid passivation is the use of citric acid to passivate stainless steel (SS) and other alloys to prevent corrosion. By removing free iron ions and forming a protective passive oxide layer on the surface, the stainless steel or other metal becomes highly resistant to rust.
How do you passivate with citric acid?
A typical formulation/process for citric acid passivation of 316 SS is as follows: Immerse the part in a 10 weight percent solution of citric acid for 30–45 minutes at 150°F. Suitable cleaning and rinsing is assumed.
What acid is used for passivation?
Nitric acid
Nitric acid is such an oxidizing acid and is always used for passivation treatments. Nitric acid does not corrode stainless steel, does not alter critically dimensioned parts and will not remove heat tint, embedded iron or other embedded surface contamination.
How long does citric acid passivation take?
Citric passivation vs. nitric passivation also offers shorter cycle times. Parts can be processed in as little as 4 minutes when using citric acid, compared to 20 minutes minimum with nitric acid.
How do you use citric acid to passivate stainless steel?
The Citric Acid Passivation Process 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.
Can aluminum be passivated?
Aluminium passivation allows this extremely ductile material to be used in a wide variety of contexts. Unlike stainless steel, aluminium does not naturally have protection against corrosion. For this reason, induced passivation is necessary in all cases.
Can you passivate titanium with citric acid?
Titanium should not even be passivated, and in citric acid is dangerous for titanium because crack corrosion can build up in the material.
What is a passivated finish?
Passivation is a widely-used metal finishing process to prevent corrosion. In stainless steel, the passivation process uses nitric acid or citric acid to remove free iron from the surface. The chemical treatment leads to a protective oxide layer that is less likely to chemically react with air and cause corrosion.