[ARC5] restoring rusty metal tubes

William Cromwell wrcromwell at gmail.com
Wed Sep 15 15:02:23 EDT 2021


Hi Dennis,

Thanks for the pointer. I know about that Rustoleum product but had not 
made the connection to use it on transformers. I have been debating 
"refurbishing" some transformers here:) I will have to remove the bells 
and replace the leads from the winding since they are cracked and 
crunchy. With your solution I will now move that forward. Those things 
are plain *ugly* at the moment. I hate to see them lost.

73,

Bill KU8H

bark less - wag more

On 9/15/21 10:52 AM, Dennis Monticelli wrote:
> There is a product made by Restoleum that is called Rust Restorer.
> https://www.rustoleum.com/product-catalog/consumer-brands/auto/removers-and-chemicals/rust-reformer-spray/ 
> <https://www.rustoleum.com/product-catalog/consumer-brands/auto/removers-and-chemicals/rust-reformer-spray/>
> https://www.rustoleum.com/MSDS/ENGLISH/248658.pdf 
> <https://www.rustoleum.com/MSDS/ENGLISH/248658.pdf>
>
> It chemically converts the rust to another more stable molecule and 
> leaves the surface flat black.  Super easy to use.  I usually just 
> spray a little on a paper towel and wipe it on.  The color changes 
> immediately.  You can paint over it if you wish.  I use it a lot on 
> transformers and chokes to improve appearance.  I recommend some steel 
> wool to first take off the loose rust and reduce the surface 
> roughness.  I'm not certain but I think it can take the heat.  Seems 
> fine on my transformers.
>
> Dennis AE6C
>
> On Wed, Sep 15, 2021 at 7:10 AM Brian Clarke 
> <brianclarke01 at optusnet.com.au <mailto:brianclarke01 at optusnet.com.au>> 
> wrote:
>
>     Hello Leslie,
>
>     The external envelope of the metal tube can reach 270°C. Ordinary
>     gloss enamel will blister and peel off. Any rust removal product
>     that uses phosphoric acid will form a coating of iron phosphate –
>     good for preventing further corrosion. But, it does reduce the
>     thickness of the metal tubing. No pot of phosphoric acid I have
>     used has mentioned survival at 270°C.
>
>     My suggestion, echoing but also eschewing advice from some of our
>     erstwhile US cousins is:
>
>     1.Test the tubes for heater continuity, emission, gain and gas.
>     Manufacturers usually understate the specifications so that
>     published figures are often less than you achieve with a NIOB
>     tube; a new tube should be at least 25% better than spec. So, any
>     tube that is not close to spec becomes a good candidate for
>     small-arms target practice.
>
>     2.Mark (scratch, engrave) the phenolic base indelibly with the
>     type nomenclature. Scratching the nomenclature into the metal tube
>     is a sure way to start later corrosion. Probably not a good idea
>     to engrave the end of the octal key, because that part often gets
>     broken off.
>
>     3.Gently remove the rust by abrading with green Nylon mesh pot
>     cleaner. Leave the old paint in place wherever you can. A wire
>     buff will remove some of the metal – where the metal is thinner it
>     will get hotter.
>
>     4.Apply a metal primer that will withstand 270°C, eg, a paint
>     designed for baking.
>
>     5.Spray on an auto engine exhaust black paint formulation that
>     will finish matt – most auto parts shops carry it. A gloss finish
>     will not radiate heat as well as a ‘black body’.
>
>     6.If you are a dab hand at calligraphy, rewrite the nomenclature
>     over the black matt with a high temperature white paint. Artist’s
>     acrylic probably won’t cut it. I got some high temperature white
>     matt from an auto parts store for redoing a toaster. Spray the
>     paint into a small pot and scribe with a fine artist’s brush or a
>     tooth pick – prefer the brush because it holds more paint; the
>     tooth pick may give a blobby result.
>
>     Cheers, Brian, VK2GCE
>
>     *From:*arc5-bounces at mailman.qth.net
>     <mailto:arc5-bounces at mailman.qth.net>
>     [mailto:arc5-bounces at mailman.qth.net
>     <mailto:arc5-bounces at mailman.qth.net>] *On Behalf Of *Leslie Smith
>     *Sent:* Wednesday, 15 September 2021 9:14 PM
>     *To:* arc5 at mailman.qth.net <mailto:arc5 at mailman.qth.net>
>     *Subject:* [ARC5] restoring rusty metal tubes
>
>     Hello all!
>
>     I bought a box full of metal tubes recently.  12A6, 12K8, 12SK7
>     and so on. Many have an unattractive amount of rust on the
>     surface, some have a small amount. None belong to a class I would
>     call 'collectable'.
>
>     Can anyone advise what I can do to preserve these?  My thoughts
>     are along the lines of clean the metal case with a buffing wheel;
>     after that re-paint with gloss spray.  All observations welcome. 
>     I would like to save a box of common, not too flash, but probably
>     quite functional metal octal tubes.
>
>     73s from Australia.
>
>     Leslie
>
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