As in the title.
Chain shoulder pads that have never left player inventory were equipped. Had 0 dmg when equipped. While equipped, they gradually rose to 1.7 dmg during combat (seen at 0.4, 1.2, 1.6 and 1.7 dmg).
No other pads I've used have taken dmg this way and I can't see any reason why these should. The wiki entry only mentions dmg taken when outside player/merchant inventory, magical chest, and mail system.
Edit:
Worth noting, this dmg (from 0 to 1.7) was taken over a period of about 30-60 min, only some of which was spent in actual combat.