March 2003

Combination of Chemical Milling (Spray Etching) and Electropolishing In Order To Structure Stainless Steel

It is well known to the PCM industry that embossed structures on the surfaces of sheet metals can be achieved by chemical milling, especially by spray etching,11-6] Unfortunately, the resulting surfaces are often dull and rough. Electrostructuring - a special kind of electro· polishing - is also a suitable way to generate embossed structures on the surfaces of sheet metals. In both processes, areas of the surface not to be removed arc covered with resist. Photoresist or screen-printing lacqucr ean be used as resist materials. Screen-printing lacquer is used if the structures arc of relatively large dimension (some millimeters). Using the electropolishing technique for structuring the surface has the advantage of making the resist uncovered areas betwccn the structures smooth and shiny; the major disadvantage of this technique is that the removal speed in electropolishing is much slowcr than in spray etching or high-pressurelhigh-temperature spray etching. Typically, electropolishing has a removal speed of 0.5 . 2 Jim/min whereas spray etching can achieve more than 100 Jim/min. Thus, the time to achieve a certain depth ofa structure by electrostructuring is much longer. Often, the stability of the resist is nOI high enough to generate a deep structure on the sheet metal surface.

M. Buhlert, Institut fur Angewandte and Physikalische Chemie