[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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