Most good airlines subscribe to the IATA fuel quality programme. If the inspections are done correctly, the fuel supplied 'at the pump' could not support CR as the filtering (C Filter) won't allow microbes through and the filter/separators won't allow water through. The problem lies with aircraft stored for any length of time or extended parking. As one contributor said - poor maintenance. Warm moist hi-humidity climates don't help, which it is more prevalent in the tropics. Biobor and regular water drains help. Purging /draining the fuel system doesn't, as the seals and sealant dry up.
Why does it eat untreated aluminium? It grows on the interface of water and JetA1 and then 'clings' to the tank interior as the levels fluctuate. It's kind of plant form which means Carbon in - Oxygen out. Water enriched with oxygen loves untreated aluminium.
Not the same but just as weird is the bottom of a plastic (fibreglass) boat. keep it in the water for three or more years and the gel coat starts to get 'eaten' - so I guess the all plastic aircraft won't be any better either
