old S&B shotgun shells corrosive?

[Farlsincharge]

I have some old #6 shells that were my fathers. I am assuming they are from around the mid 80's. They are sellier and bellot with a black hull and were sold through the co-op. On the side they say "Plastik", 6, 70.
Headstamp SBP (with a circular symbol on each side) made in chechoslovakia. Primer says SBP with three stars.

Anyone have any insight as to wether or not these could be corrosive?

 

[CanadianAR]

I shot some S & B from when they sponsered the olympics in the mid 70s, I haven't cleaned the gun since and there is no corrosion. (2 months ago) I know I am a monster. Just not one I care about.