Charger issues. Fluid at the end of charger

Overnight Iphone 5S stopped charging. Got an error that the charging wire is not compatible although it was original wire. Tried different outlets without success. Bought a new apple charging wire from radioshack which did not work. Then noticed that what looked corrosion at the charging port and liquid stains similar to what you would expect if an old battery was leaking. Took it to Apple store and they claimed that battery was fine, there was no damage or fluid inside. Claimed that this was considered accidental damage and not covered by warranty. Had to pay 270$ for a new phone. See images for damage to original phone. When I returned home, I found that the charger end that goes in to port has also been damaged.

Now been using new iphone with new apple charge for the last 10 days. Also have been using a power strip with surge protector. Went to plug in the phone last night and noticed the charger end was damaged and had sticky oily fluid on it. Also had sticky fluid on the floor where it was lying. The end looks as if it was burnt or corroded. See the images.

I am positive that phone or charger was not exposed to humidity or liquids. Same problem occurring twice in 2 weeks with different sets of phone and chargers. What could be the issue?