Why is my device not charging?

I recently purchased an iPhone 4 that has had water damage. After having a friend who repairs all sorts of apple products look at it, he though just the battery need replaced due to the corrosion on the terminals. After ordering and replacing the battery i plugged phone in to iTunes and factory reset it. Shortly after i noticed the phone was not taking a charge, although it was plugged in and the device recognized that. Thinking i had a faulty battery i replaced it a second time and had the same results. The device syncs and transfers data just like any other iPhone would just doesn't charge. I have even tried multiple transfer cables, different computers and different wall outlets. No luck. both the dock water damage indicator and the one inside on the lower half (beside battery connector cable) have turned red. I am wondering if replacing the dock connector on the phone will solve my problem, or if my phone is shot. I cant see it being much more because everything works like it is supposed to other than it doesn't charge.