Pickling
Pickling is very similar to the passivation process in that a bath of acidic chemicals is used to enhance the surface of the stainless steel. However, pickling uses a more intensive chemical mixture, with may include nitric, hydrofluoric, hydrochloric, and/or sulfuric acids. This stronger combination strips the surface layer of the steel, removing a thin layer of the metal, including any impurities, scale, weld burns (heat tint), and free iron—leaving an even, satin-like finish.[1][2][3][4][5][6] Pickling is a very imprecise process, with many drawbacks, and it is also very difficult to create consistent results as the amount of surface material removed can vary greatly.[7] Pickling does not enrich surface chromium, and therefore does not provide the same function of a passivation treatment.[8]
Electropolishing is a useful alternative to pickling. Metal removal is achieved, but usually results in a bright, smooth and more highly corrosion resistant finish.[9]
Fortunately, neither pickling nor electropolishing need to be used by home brewers. Besides being easier and safer, passivation treatment and proper care of stainless steel provides very high corrosion resistance and off-flavor prevention.
See also[edit]
References[edit]
- ↑ "Your Guide to Stainless Steel Passivation." Marlin Steel Wire Products, 2020.
- ↑ Crookes, R. Pickling and Passivating Stainless Steel. Second Edition, Euro Inox, 2007. ISBN 978-2-87997-224-4
- ↑ "Stainless Steel Pickling." Delstar Metal Finishing, Inc., Retrieved online June 2020.
- ↑ "Passivation & Pickling." Harrison Electropolishing, Retrieved online June 2020.
- ↑ "What Is Pickling & Passivation." Central Electropolishing Co., Inc., Retrieved online June 2020.
- ↑ ASTM A967 / A967M-17 "Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts." ASTM International, 2017, www.astm.org
- ↑ "What is Pickling for Stainless Steel?" Able Electropolishing, Retrieved online June 2020.
- ↑ Wegrelius, L., and Sjödén, B. "Passivation Treatment of Stainless Steel" Acom, no. 4, 2004.
- ↑ "Pickling and Passivation." Australian Stainless Steel Development Association (ASSDA), Retrieved online June 2020.