Passivation: Difference between revisions

Passivation (edit)

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 [[File:Rusty-stainless.jpg|thumb|Rust on a new stainless kettle]]
-[[Stainless steel]] equipment purchased by home brewers is often not passivated (to a degree that chemical passivation can accomplish), as evidenced by the frequent presence of machine oils and/or rust spots on brand new equipment.<ref name=lawrence>Lawrence, G. [https://countrymaltgroup.com/what-is-tank-passivation/ "What is Tank Passivation?"] Country Malt Group, 2018.</ref> Often stainless steel is [[pickling|pickled]] by the manufacturer, which does not provide the degree of surface chromium enrichment that passivation does.<ref name=wegrelius/> Also, welding and physical abrasion during manufacturing or transportation removes the effect of any previous passivation or pickling in the affected areas, even if the steel had been passivated at some point earlier in the process.
+New [[stainless steel]] equipment is often not passivated (to a degree that chemical passivation can accomplish), as evidenced by the frequent presence of machine oils and/or rust spots on brand new equipment.<ref name=lawrence>Lawrence, G. [https://countrymaltgroup.com/what-is-tank-passivation/ "What is Tank Passivation?"] Country Malt Group, 2018.</ref> Often stainless steel is [[pickling|pickled]] by the manufacturer, which does not provide the degree of surface chromium enrichment that passivation does.<ref name=wegrelius/> Also, welding and physical abrasion during manufacturing or transportation removes the effect of any previous passivation or pickling in the affected areas, even if the steel had been passivated at some point earlier in the process.
 Passivation treatment is not just beneficial for new equipment. The thin chromium rich layer can erode under normal usage conditions, necessitating that the equipment be passivated periodically.<ref name=sanimarc>Allard, D. [http://sanimag.sanimarc.com/passivation-natural-protection-for-stainless-steel/ "Passivation – Natural Protection for Stainless Steel."] Sani Marc Group, 2015.</ref><ref name=cluett>Cluett, JD. [https://ujcontent.uj.ac.za/vital/access/services/Download/uj:14727/CONTENT1 "Cleanability of Certain Stainless Steel Surface Finished in the Brewing Process."] Dissertation, 2001.</ref> Stainless steel is not immune to physical or chemical attack from conditions in the home brewing environment. Chloride or chlorine compounds in water sources, acid sanitizers, organic acids (e.g. in wine or [[sour beer]]), and carbon dioxide dissolved in the beer (or other fermentation) all chemically attack stainless steel over time.<ref name=lawrence/><ref name="MB">Palmer, J. [https://www.morebeer.com/articles/preventing_corrosion_in_your_brewery "Preventing Corrosion In The Brewery."] MoreBeer, 2015, (originally published in ''Brewing Techniques'', year unknown).</ref><ref name=kilkeary/><ref name=mbaa/> An existing chromium-rich passive layer can also be damaged or removed by physical abrasion or scraping. In fact, stainless steel is relatively easy to scratch, which may be caused by use of abrasive cleaning pads, cleaning products, and contact with other metal tools. Many household cleaning products are abrasive, such as Comet, Ajax, Barkeeper’s Friend (BKF), and Soft Scrub. All of these products are capable of scratching stainless surfaces and should usually be avoided.<ref name=byo>Green, D. [https://byo.com/article/stainless-steel-care-tips-from-the-pros/ "Stainless Steel Care: Tips From the Pros."] Brew Your Own, 2018.</ref> The passive layer can also be weakened by physical damage due to expansion and contraction caused by heating and cooling.<ref name="Diversey"/>