Page 48 - PCMI Journal July 2018

David Allen | Emeritus Professor | Cranfield University | UK Photochemical Machining of Aerospace Materials
5/31/18
What is Hydrofluoric Acid (HF)?
HF is a volatile liquid with a boiling point of 19.5°C
and is normally sold as an aqueous solution at the
following typical strengths in the UK:
• 40% by wt (equivalent to 22.6M or 22.6N) (Specified Laboratory Reagent and Analytical grades)
• 48% by wt (Analytical grade)
• 46-53% by wt (doubly-distilled Analytical grade)
• 58-62% by wt (Technical grade)
Limitations of HF as an industrial etchant
Although HF is a dangerous etchant, it is much used in industry for;
• Microelectronics fabrication
• Chemical milling
• Photochemical machining
• Decorative etching and structuring of glasses and
ceramics
and even in
• Car trim cleaning!
Issue 131 July 2018 PCMI Journal 47
4