Page 28 - PCMI Summer Journal 2021
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The Chemistry and Control of Etching Ferrous Metals with Ferric Chloride Solutions: The Concept of a Constant Etchant Pool Presented by: David M. Allen, Emeritus Professor of Microengineering, Cranfield University, UK
Figure 9. Ferric chloride regeneration processes and by-products (boxed in red).
Figure 10. Regeneration by-product build-up.
Practical details of regeneration systems have been provided recently by Lauver [6]. However, irrespective of the regeneration system used, the chemical oxidation of Fe2+ to Fe3+ is always triggered by monitoring ORP. Upper and lower limits for ORP are fixed and when the ORP drops to the set lower limit the oxidation process is started. As the [Fe2+] reduces and [Fe3+] increases, the ORP increases and once the ORP reaches its set upper limit the oxidation
Issue 137 August 2021 PCMI Journal 28
