Hydrofluoric acid/ammonium orthophosphate

The effect of etch time (30 sec vs. 180 sec) on the composition of a Ti-6-4 surface etched in hydrofluoric acid/ammonium orthophosphate solution was followed by two SIMS spectra shown in Figure 29.(33) The aluminum signal decreases with increasing etch time while the vanadium signal increases. Preferential etching of the aluminum-rich a phase relative to the vanadium-rich p phase by the etch leads to the decreased aluminum signal. 

FIGURE 29. SIMS spectra of titanium-6-4 etched in hydrofluoric acid/ammonium orthophosphate for 30 sec (b) and titanium-6-4 etched in the same acid mixture for 180 sec (a). Reprinted with permission from Reference 33. Copyright 1981 Gordon and Breach Science Publishers. 

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