Magically enhanced by one of the Chaos powers, Chaos Armour may be taken as an upgrade for a model wearing power armour, increasing the save to 2+. Note that although Chaos armour gives the same protection as Terminator armour, items that are 'Terminators only' may not be used with it.
Chaos Armour
Source: Codex: Chaos Space Marines (1999), p. 20