Great point. You would not store binary weapons in the warhead until hostilities were imminent. Seepage, leaks and deterioration would likely cause many to have a very bad day. The existence of these warheads is real evidence.
I'm at work. Is there any indication as to the caliber of the warheads? The Iraqis possess a very good South African 155 which has excellent range. It also has little use for these warheads to hurl anything other than CW. They're not going to throw smoke or CS with their 155s. Of course if the warheads are missle types that should be the ballgane.
The articles above say 122 mm shells. According to this site, that's a pretty common weapon for the Iraqi army.
These guns are probably variants of the Russian Layagushka artillery piece.
Many chemical warheads are also caustic or acidic, and corrode metals.