Anodizing aluminum at real high current density will also make it very brittle. Your 5657 alloy is used for MIG welding aluminum not soldering, like other 5xxx series alloys it does anodize well.
If your 3-5 amps is actually correct (doubtfull if your are reading it on the "ammeter" of a battery charger) the wire would have to be very long and a very large diameter to not be being at way too high a current density. If you provide the length and diameter of the wire the current density can be easily calculated.
If you're interested in anodizing the right way, download and read this:
http://caswellplating.com/kits/lcd_ano.pdf