[TowerTalk] Cleaning aluminum tubing.

[Wes]

I've written about this several times over the years; here it is again. I used 
to buy defunct beams, and frequent a metals scrap yard to acquire material for 
experimental beams.  Invariably, the stuff needed cleaning and abrasion of these 
quantities was too much work.  So I adopted part of a method that was used in my 
employer's engineering fab shop to passivate (Alodine) aluminum.

In a nutshell, a strong caustic (lye) is used to attack surface oxidation and 
other gunk, after that a water rinse followed by an mild acid wash to neutralize 
any leftover lye and a final water wash and drying results in a nice slightly 
etched/satin surface.

I do this outside by building a trough out of 2x4s or other scrap lumber lined 
with heavy plastic sheet. Make this long enough to handle the longest length of 
tubing.  I use ordinary household lye that is back on the market now that meth 
users can get their stuff from Mexico instead of cooking it themselves.  Of 
course, I use gloves and eye protection.  Experiment with the concentration; 
some fizzing should be evident at first.  This will subside as the mixture wears 
out so you might have to freshen it up.  Depending on the alloy there will be 
some darkening of the surface but this will wipe/rinse right off.  I keep a 
garden hose running to rinse the work and to use in the case of a splash onto 
me.  Ordinary white vinegar of Costco gallon jug variety will finish the process 
and help remove any leftover smut.  Be sure to rinse with water both inside and 
out and you're done.

Dispose of the leftovers carefully.  Out here in the desert I just pour it on 
the ground; in more civilized surrounds you might want to use it as drain cleaner.

Use this at your own risk.

ps. If you homebrew equipment and build your own boxes a method I've used is to 
make everything out of flat sheet with corner blocks.  A random orbit sander, 
sometimes used with a lubricant, can give a lovely "brushed" surface effect if 
followed by etching by the above method.  See my QRZ page amplifier photos for 
examples.

Wes  N7WS