What is the limit of Cl2 and Cl- in process water used in a fermentation process at both process and corrosion point of views? Generally speaking, I would like to know what range of Cl2 and Cl- is permitted to prevent corrosion in 304 stainless steel fermenters and to avoid the yeast degradation in a baker yeast production plant.
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Brian Dalder Forum Moderator 177 Posts
Re: Can you help with corrosion caused by chlorinated water?4 October 2011 at 1:29pmI can help with corrosion caused by chlorinated water and chlorides but as to their effect on yeast degradation you are on your own! Chlorides are problematic with austenitic stainless steels like 304 as they can cause pitting, crevice corrosion, and stress corrosion cracking. Temperatures above ambient and cycling between hot and cold temperatures can make corrosion worse as concentration of chlorides due to evaporation an occur. The generally recommended maximum chloride level for 304 stainless steel is only 200 ppm (1000 ppm for 316 stainless steel). The low free chlorine levels of typical potable water systems will not affect austenitic stainless steels. However, free chlorine concentrations of as little as 25 ppm can have a detrimental effect on them. The subject of chloride induced corrosion of austenitic stainless steels is very complex and depends on many things such as concentration, temperature, pH, etc. Fortunately, this subject has been studied extensively and there is much information available to help answer your questions. One place you can start is with the nonprofit organization, the Nickel Institute (http://www.nickelinstitute.org), which has numerous technical publications on stainless steels and corrosion that you can download free of charge.