Case that don't corrode your iPhone

[GSA190]

I currently have the iCase slider iphone 3g case. I hate it. Dust collects inside of it every day and corrodes the outer shell of the iphone. I really want a case that would greatly decrease the corroding and eliminate it completly. Can someone suggest a iPhone 3G S case?

[The Apple]

I use the Otterbox Defender. The defender has protection all the way around. It covers all openings so less dust will get in. It is a little more expensive than others, but it does a great job.