[ARC5] restoring rusty metal tubes

[Dennis Monticelli]

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/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>
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]
> *On Behalf Of *Leslie Smith
> *Sent:* Wednesday, 15 September 2021 9:14 PM
> *To:* 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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