My solution .. use a plastic scrubber housing :
OK..I know I shouldn't... but couldn't help it!!
Seriously, hope you are taking the same precautions with your Aluminium cylinders and not simply putting steel bands around them. You need to put a rubber layer between the two different metals otherwise the type of corrosion you have found is a great way to knacker the cylinder in a very short period of time. Please tell me you were aware of that already!!!
Steve