Compressed air impact wrench for wheel change

Hi guys, I’ve been changing my wheels for some time. So far I’ve always taken the good old wheel cross to loosen the screws. Since I’ve been allowed to call a compressor my property for almost a year, I bought a compressed air impact wrench in the bay (in the set with other compressed air tools for not all too much money). Today I wanted to use this thing for the first time. Set 6 bar on the compressor, put the impact wrench and… But the screws didn’t move in mm. I then increased the pressure to 10 bar (max. pressure of my compressor), but it didn’t happen again. I thought that the screws were kind of rusty, but with the wheel cross I could unscrew the screws without any problems. Do I suppose that this thing is just scrap or do I need “more power” (hear who hammers there)? And what do you buy from compressed air punches? Robbing?