Yes, it likely IS corrosive. All Warsaw Pact ammo from the period generally is.
And every round fired by all sides in WW 2 EXCEPT M1 Carbine was also corrosive. No big deal. After shooting, pour a quart of hot water thru the barrel, 2 drops of dawn dish detergent on bore brush, scrub the bore, pour another qt of hot water thru the bore, let sit for 5 minutes, dry patch, oiled patch, done.