I think we've covered that a barrage of cold magic or fireballs on armor, shields, and weapons would compromise their durability in different ways and potentially harm the user, but I don't recall talk of a very particular facet of how it affects equipment. A superheated shield, regardless of whether it was caused by an enemy or the wielder, is still glowing with heat, potentially enough to use against a mage and ignite them with a well placed shield bash, or glue exposed flesh to a cold shield, shock a wet opponent, etc. Those lingering effects would be, by nature, indiscriminate.
We can take this a bit further, as well. A chilled shield or armor piece against a red hot sword is likely to cause thermal shock and cause cracking and chipping between both pieces of equipment. An electrically charged shield that is insulated may hold a charge long enough to be discharged back into an opponent's metal armor, or cause the opponent's sword to stick to your shield after it's hit with a gravity ball, or cause your cold shield to stick to their armor and leave you vulnerable.
These residual effects would result in some rather interesting dynamics in combat I suspect, especially when there are magic users on both sides of a conflict.
Is this at all in line with what you have planned or want to do? Any plans in this vein that are different from this approach?