All you need is to keep it free of obvious debris and organic material. Just scrub it down before use and stick it into your BK during the final 10-15 mins of your boil. That will effectively sanitize it and when your done chilling, pull it out and give it a rinse and maybe another quick scrub before storage. Cupric oxide (aka the green patina seen on such famous statues as Lady Liberty and lots of domed roofs) is the only thing that can cause issues, but if you keep it clean and free of debris it should be fine and won't develop anything like that. For that to develop, you'd have to have an active galvanic reaction taking place with your wort chiller, which you'd be hard pressed to see happen indoors in someone's home.