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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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citric acid Passivation of Coffee Brewing Water Tanks
Q. My question has to do with the passivation of stainless steel tanks used to heat water for coffee brewing applications. When installing brand new factory equipment, often the first brews of coffee come out with a metallic taste.. This phenomena gradually gets less with use of the equipment, but never really goes away entirely.. I would be interested to know if citric acid passivation of the tanks before installation would eliminate this or reduce the metallic taste that the heated water acquires.. I worked in the metal finishing business for about 5 years and have a basic idea of the process required to accomplish this. Any ideas or direction would be greatly appreciated.
Anthony Makelaa specialty coffee co. - Minneapolis, Minnesota, USA
2003
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A. Dear Anthony: I guess you are on the right track, In Denmark we use nitric acid for passivation, Americans use as you describe citric acid . Both will take the metallic taste. Best Regards, Bo Kønig- Denmark 2003 A. Yes, citric acid passivation with the correct formulations will definitely remove the taste of the iron on the surface of the steel in the initial brews. If you want to try this let us know and we will get samples to you for testing. It would be a simple task.   Lee Kremer Stellar Solutions, Inc.  McHenry, Illinois  2003 |
A. If I were to guess I would say that some of the fittings are 303 stainless steel. 303 has sulfur in it to make more machining friendly, but can have the effect of leaching sulfur into the product. We passivate parts and have to pass the "Coke Test" This is because of 303 and the test will detect residual sulfur. Citric would be a good call, contact Lee Kreamer at Stellar Solutions [a finishing.com supporting advertiser].
Jon Quirt- Minneapolis, Minnesota
2003
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