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[TowerTalk] Cleaning aluminum tubing.

To: Tower Talk <towertalk@contesting.com>
Subject: [TowerTalk] Cleaning aluminum tubing.
From: Wes <wes_n7ws@triconet.org>
Date: Fri, 19 Jul 2019 18:19:11 -0700
List-post: <mailto:towertalk@contesting.com>
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

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