nal was observed from the oxide layer over the matrix.
In general, steam treatment of AA1090 and AA6060 with aqueous HNO3 solution of pH 3.0 (Figs. 7(b) and 8(b)) and pH 2.0 (Figs. 7(d) and 8(d)) produced oxide layer with needle like morphology similar to Peraluman 706TM. Further, under steam conditions (pH 3.0), cell size on AA1090 and AA6060 was similar to that on
Peraluman 706TM, while under steam conditions (pH 2.0) AA6060 showed distinct cell structure. Nevertheless, in all cases N signal was detected at the intermetallic particles present in AA1090 and AA6060 irrespective of the difference in pH of HNO3 as shown in Figs. 7(a) and 8(a)