About a month ago the Apple Lightning to USB cable (PN: MD818ZM/A, $19) that I keep in my vehicle for charging my iPhone 5s began to fail. At first charging was intermittent, then within a week the cable wouldn't charge my iPhone at all. A closer look at the male end of the Apple Lightning to USB cable reveals that several of the gold contacts have become corroded.
A check of Apple's discussion forums reveals that other users have had issues with corroded lightning cables. Experiences with Apple support representatives vary, with some users being accused of liquid damage (which isn't covered by Apple's warranty) while others have had their cables replaced without issue.
Apple Discussions user "brockap3" noticed that the corrosion is happening mainly on the VBUS/V++/Power providing pin of his Lightning cable (here's an image of the pinouts of the lightning connector). He offered two possible scenarios:
Two gold electrodes placed in an aqueous solution with a positive voltage on one wire and ground applied to the other will corrode the positive gold electrode away
Electrical arcing causing the corrosion (originally I dismissed this as it is just USB - i.e. 5 V /2 A max)
Brockap3 posted photos of the corrosion on his Lightning cable taken with a microscope:
In my case, both my wife and my Lightning cables failed due to corrosion within a month of each other. Both iPhones were purchased at launch (September 20, 2013) making them just over five months old. Luckily we purchased both iPhones with AppleCare+ and the Apple retail representative I spoke with by telephone recommended that I make an appointment to bring the cables in to the Genius bar. I'll update this post with the result of my visit.
Update 2014-0305: Anecdotal evidence from reader emails indicate that these failures seem to be more prevalent in wet/moist climates and of cables kept in a vehicle. If the Lightning end of the cable is dropped onto/dipped into a wet or snowy floor mat (while plugged into a vehicle’s 12 volt power outlet) it can arc/short the cable (and even the device!) if plugged in while the end of the cable is still damp. My local Apple Store replaced both corroded Lightning cables, no questions asked (although both iPhones have AppleCare+).
Have you had a corrosion issue with an Apple Lightning cable?