Passivation: Difference between revisions

Citric acid is a powerful metal complexing agent (the chemistry term is chelation - key-LAY-shun). This causes it to dissolve iron from the stainless steel surface and also complex with iron in solution, all while sparring the chromium and other metals.<ref name=mazinanian/><ref name=kilkeary>Kilkeary, JJ, and Sowell, T. [https://astropak.com/wp-content/uploads/2014/07/New-Developments-in-Passivation.pdf "New Developments In Passivation Technology."] Astro Pak Corporation, Presented at Interphex Pharmaceutical Conference, 1999.</ref><ref name=olaoire>O'Laoire, C., et al. [https://www.tandfonline.com/doi/abs/10.1080/00032710600755363 "Analysis of the Acid Passivation of Stainless Steel."] ''Analytical Letters'', vol. 39, no. 11, 2006, pp. 2255–2271.</ref><ref name="Diversey"/><ref name=Kremer/><ref name=allegheny/><ref name=Olsson>Olsson, H., et al. [https://www.mbaa.com/publications/tq/tqPastIssues/1983/Abstracts/tq83ab06.htm "Stainless steel flavour contribution to beer."] MBAA TQ vol. 20, no. 3, 1983, pp. 102–105.</ref> Besides removing surface iron, citric acid passivation also works to remove sulfide inclusions, which are implicated in causing pitting corrosion.<ref name=bragaglia/> Citric acid is not hazardous, it does not cause any corrosion or etching, and it is suitable to passivate all types of stainless steel.<ref name=a967/><ref name=Speranzini>Speranzini, RA, et al. [https://www.corrosionjournal.org/doi/abs/10.5006/1.3583842 "Corrosiveness of Decontamination Solutions to Sensitized AISI 304 Stainless Steel."] ''Corrosion'', vol. 43, no. 10, 1987, pp. 632–641.</ref><ref name=usa/><ref name=olaoire/>