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"Citric Acid for stripping galvanizing?"
October 14, 2015
Q. Citric acid will strip zinc (galvanizing) off steel, slightly slower than HCl or H2SO4, but the liquid product might be easier to dispose of.
Has anyone done this commercially? If not any specific reason?
What might the disadvantages be of considering this process for stripping old or faulty galvanizing?
Westfield, Scotland, UK
November 17, 2015
A. The disadvantages are: (1) Citric Acid is much more expensive; (2) From my considerable experience with citric acid, zinc, and mineral acids, it reacts much, much more slowly than strong mineral acids (time is money!), and (3) it is a complexing agent (which may or may not be a disadvantage). For much of hot-dip galvanizing (that part of the industry using Prime Western Zinc), hydrochloric acid is the best choice, since it will dissolve not only the zinc but the lead (up to 1.4% w/w) as well, as lead sulfate is insoluble.
CTO - Jackson, Michigan, USA