Help me understand - strings breaking due to corrosion

[ba4x]

Hi Folks

My dad has an old 1967 Klein G6 classical guitar. He doesn't play it too much anymore, but every 6 or 8 months when I visit, I check up on it and play it for a few days. We're trying to keep it in good shape.

Lately it's developed a strange pattern. Every time I come home to visit, a string is broken. It's typically the D string. For a while I though this wasn't too odd, humidity or temperature changes could have caused it. I bought him a nice hard shell case, and now, even with the guitar in case 24/7, the string is still broken. It's reliable, I can expect it every 6 months. The climate here (MI) is humid in the summer, but the house is climate controlled and not really extreme.

Upon looking closer, I see some serious corrosion/oxidation going on at the nut. There's all this green powder collecting around the wound strings in the nut slots. The entirely of the string (other than that location) is clean and free from the green stuff.

What could it be? Is the string reacting with the nut material?

A few years ago the guitar went in for some repairs. Directly after this, the string breaking pattern began. I wonder if they re-glued the nut at that time, and the new nut or glue is causing the issue. I am not sure if they did any work on the nut, and it's too late to ask now (shop closed down).

The strings are EJ45s. To quote D'Addario: Pro-Arté basses are wound using silver-plated copper on a multi-filament nylon core. I think it's copper that's giving the green powder.

Any tips? Anyone see this before?

[Bax Burgess]

When a string has broken, do you replace the whole set or just that one string?

Is there a burr on the zero fret?

[DownUpDave]

I am wondering if they filled the nut slot with baking powder and crazy glue (or something else), then recut the slot. This is a common fix for a nut slot cut too deep and string buzz. It definitely looks like the wound strings are reacting to something at the nut. Maybe repost this in the luthiers subfourm, those people should know.

[ba4x]

Thank you guys for the replies!

In the past I've changed all the strings at once, and also replaced them individually. I like the idea that the lingering corrosion could accelerate the reaction in a fresh string, but it seems to happen even without the help.

The zero fret raises some questions but I don't see an obvious burr or sharp edge on it.

I posted this topic in another discussion group, and among the replies someone pointed out the possibility of electrolytic corrosion. I am leaning this way in my reasoning now. The copper in the string is held against the brass fret (could be brass, not entirely sure), with the silver winding in between. This could facilitate the exchange of electrons, lead to oxidation and corrosion. The zero fret does look very dark, as if it's oxidized much more than the others. The zero fret also looks different than the other frets, the ends are trimmed differently. Maybe it was replaced at one point.

Of course humidity will accelerate this process, so watching moisture levels is a good strategy anyways. I need a few more days to dust off my high school chemistry and understand this better.

[Edgar Poe]

I see severe corrosion at the nut AND Zero Fret.
I would suspect the cleaning solution being used is not made for guitars.
I would remove the strings, give the guitar a good cleaning with a GUITAR cleaning solution and then install new strings.
I bet the problem stops.

Ed

[redir]

I've seen this green corrosion before. I'm not really sure what it is but some people literally sweat out acid. So I always thought that's where it came from.

[Howard Emerson]

Originally Posted by ba4x

Thank you guys for the replies!

In the past I've changed all the strings at once, and also replaced them individually. I like the idea that the lingering corrosion could accelerate the reaction in a fresh string, but it seems to happen even without the help.

The zero fret raises some questions but I don't see an obvious burr or sharp edge on it.

I posted this topic in another discussion group, and among the replies someone pointed out the possibility of electrolytic corrosion. I am leaning this way in my reasoning now. The copper in the string is held against the brass fret (could be brass, not entirely sure), with the silver winding in between. This could facilitate the exchange of electrons, lead to oxidation and corrosion. The zero fret does look very dark, as if it's oxidized much more than the others. The zero fret also looks different than the other frets, the ends are trimmed differently. Maybe it was replaced at one point.

Of course humidity will accelerate this process, so watching moisture levels is a good strategy anyways. I need a few more days to dust off my high school chemistry and understand this better.

You're correct regarding the electrolytic corrosion.

That's exactly why the zero fret is so dark.

Perhaps a stainless steel fret would help, but I don't know chemistry.

If the zero fret was removed, and replaced with a bone platform with longitudinal 'bump' (forming a 'fret'), you would not have these issues any more.

It would be a little inelegant looking, but it would work, and negate having to make a very 'long' nut.

Regards,
Howard Emerson

[Rapido Eduwardo]

I does appear to be electrolytic corrosion, same as appears on a battery terminal. The fix for a car battery with this condition is to clean off the copper oxide and put cup grease on the terminal. I would try a microscopic drop of guitar oil available in many guitar supplies stores. If you are so inclined, clean the copper oxide off and put a small drop of oil on the nut. Don't see how this could possibly hurt. I am not a guitar tech so take this with that caveat.

Good luck.