Corrosion inhibitors

In 1976 John A Betts wrote about benzotriazole, a corrosion inhibitor for alloys with high copper content (FoMRHI Comm. 23). I included his notes in the plain text attachment. (sorry for the “??” indicators, I’m sure the original PDF is available online.)

Another “-azole” inhibitor was the topic of Ben Krasnow’s Youtube video “How corrosion inhibitors protect metal” (2019). Check out his Youtube channel, there are some very interesting (advanced) experiments. In this particular video, he goes through the process of testing and making one based on clues from patent US4193882.
It was “DeOxit”, which also acts as a surface cleaner, that triggered his curiosity.
This is in contrast to benzotriazole, which acording to Betts “is not a copper cleaner and is completely ineffective for this purpose” as “it will stabilise tarnish”.

Krasnow explains how the sulfur acts as an anchor for oil to attach to the surface of metal. Given that these molecules chemically form a very thin, inert, insoluble, invisible layer they sure are ideal for treating harpsichord strings. Judging from the lack of visible corrosion on 6-year-old spools of Rose and Stolberg strings I have carelessly stored, my guess is that harpsichord strings were already treated this way. Is this true?

Do you think that this is a better alternative to the commonly used mechanical barrier created by quenching tuning pins in oil? Should’ we also treat hitch- and bridgepins? Do you know more about this topic? Let me know!


Ben Krasnow’s channel

Traffic on this site I created seems to have gone to zero, which is pretty disappointing. In case you think there is nobody here, I will offer a quick comment.

Most people get by fine without corrosion inhibitors. Why is this a problem for you? What is your environmental situation? A good dry room with reasonable humidity, strings and pins will last decades without significant corrosion. If iron strings rust, steel wool fixes that in a jiffy. Maybe it’s pretty dry down here in Australia but I have never seen corroded hitchpins or bridge pins.

I am not an industrial chemist but I know there are a vast number of corrosion inhibitor products on the market. There’s a very well known and effective one in Australia called G15. But personally I would never put anything on the strings. I use traditional Japanese Camellia Oil on my saws and hand tools.

I have no evidence but I would say the closest your wire manufactures get to protecting the iron wire is to wrap the spools in commonly available brown paper with rust inhibitor infused into it. Even taking them ourt of the paper we just keep our spools in a metal box and they suffer no corrosion even after many years.

So tell us more about the issues you are facing.

I see them all the time in pianos here in Hilo, Hawaii, where it is constantly damp and the air is full of salt from the churning of the Pacific Ocean. My own fingers rust and corrode over night while I sleep.

When laying on new strings, I wipe them with a bit of greasy sheep wool.

Yes here in Melbourne the air blows across 10,000 km or so of red desert from the north, and it is a very dry climate. Must be the opposite of Hawaii!

Here in Ireland (like Hawaii but probably less salty) the air has blown across several thousand miles of ocean. Soundboards get mould spots, etc but are not inclined to split as much. The tip with raw sheep’s wool is good, thanks, must do that!

There are many other areas where it gets very humid, and Carey Beebe’s helpful harpsichord website (search terms strings, rust) discusses some problems - he notes that strings are far more inclined to corrode on their upper surfaces. So the sheep’s-wool treatment could also help where the strings are already in place. He also notes that because wood is acidic, it can help to seal it with shellac around the string contact points at bridge and nut before restringing (especially in humid climates).

I’d be careful with the steel wool- escaping rust dust might stain the soundboard while the steel wool is abrading the string. If you rotate the instrument 90° or even 180° so the soundboard is vertical or above, then more rust particles would fall to the side rather than onto the soundboard. I assume that removing visible rust marks on iron strings is mainly cosmetic and the sheep’s wool treatment could also help protect/seal with the rust marks still in place.

Thanks for the replies. Sorry, I didn’t include the proper links:

Ben Krasnow’s Youtube channel (really recommended!)

How corrosion inhibitors protect metal

FomRHI issue with “Some Notes On The Use Of Benzotriazole…”