Right First Time – Photochemical Machining of Stainless Steels via Control of Ferric Chloride Chemistry
The etching of stainless steels is a mainstay of photochemical machining (PCM) commerce
worldwide. However, as a class of materials designed to be corrosion-resistant, stainless steels are
not easy to etch. This paper discusses the complex nature of ferric chloride etchant used to etch
stainless steels and the control of its chemistry. In particular, the effects of changes in etchant
concentration and temperature, free hydrochloric acid, dissolved by-products and spray pressure
and distribution are analysed with respect to achieving a viable etch rate and an acceptable surface
finish in a range of commercial stainless steels.
