Read about "water break" testing and solvent cleaning.

http://www.lmaeronautics.com/materia...docs/pg054.pdf
http://www.westsystem.com/ewmag/20/Contamination.html

These two documents have information on surface preparation for bonding.

I built several glued together aluminum fuel tanks and discovered that I
could consistently make a glue joint fail if I wiped the joint surfaces
with acetone or alcohol after etching and rinsing with water. So I
stopped solvent wiping. I never tried MEK.

Here are two of my tanks:

http://home.teleport.com/~guynoir/re...edinterior.JPG