Alkaline hexacyanoferrate etch soln. - contains a silicate for etching and forming chromium, molybdenum and tungsten

摘要

Layers of articles or Cr. Mo and W are etched using a directionally controlled etching procedure and a silicate contg., buffered, alkaline hexacyanoferrate (III) soln. as etching medium. The soln. is directed onto the metal at right angle to the surface to be etched, pref. under pressure. A soluble alkali silicate is used as silicate addn. in an amt. of 0.1-500 g/l (10-100 g/l) and an alkali oxalate, pref. Na oxalate as buffer in an amt. of 5-10 g/l. The soln. is used at a temp. of 40-60 degrees C (50 degrees C). With silicate in the etching soln., and with directionally controlled etching procedure, a tough coating of hydrated silicic acid is formed which is more rapidly destroyed in the etch pit than at the shoulder resulting in a more accurately defined structure.