Fabrication of microchannels on stainless steel by wet chemical etching

Microchannels in stainless steel were fabricated by using solutions of various concentrations of FeCl3, HCl and HNO3 in water as etchants. This study shows that for obtaining smooth uniform channels on stainless steel substrates, an etchant consisting of FeCl3, HCl and HNO3 is necessary. An increase in the concentration of HCl in the etchant increases the etch rate as well as the etch factor but adversely affects the roughness. Addition of HNO3 is necessary to obtain smooth uniform channels. The depth and etch factor are significantly affected by the composition of etchant, operating temperature and initial width of opening. In the range of operating conditions studied, an etchant containing 10 wt% FeCl3, 10 wt% HCl and 5 wt% HNO3 at 40 °C and an initial width of 190 µm gave the best results. With this etchant, the channels were smooth and uniform without any cavities on the edges of the channels. Initial width also plays a vital role in obtaining the final desired depth and etch factor.