Effects of HNO_3 concentration on the pit morphologies of aluminum foil etched in HNO_3–HCl and HNO_3–H_2SO_4–HCl solutions

摘要

In this work,the effects of HNO_3 concentration on the pit morphologies of high-cubic-texture aluminum foil etched in HNO_3-HCl and HNO_3-H_2SO_4-HCl solutions were investigated.When the aluminum foil was etched in HNO_3-HCl solutions,the morphologies of pits transformed from irregular tunnels to typical tunnels(as inverted pyramids) and shallow cuboids as the HNO_3 concentration in the etchant solution was increased.However,as the HCl concentration in the etchant solution was increased,the morphologies of pits transformed from shallow cuboids to typical tunnels(as inverted pyramids) and irregular tunnels.When the aluminum foil was etched in n N HNO_3-(7.2-n) N H_2SO_4-0.8 N HCl solutions,the morphologies of the pits transformed from typical tunnels(i.e.,the number of sub-tunnels formed on the main tunnels increased) to irregular tunnels(corrugated tunnels and polyline tunnels) as the HNO_3 concentration in the etchant solution was increased.These effects are attributed primarily to corrosion on the(100) and(010) faces of pits being accelerated and to the(001) faces being prone to passivation to different degrees when various concentrations of HNO_3 are added to the etchant solutions.