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Discussion Starter · #1 ·
In another thread about lacquer on a YAS-21, I checked my YTS-21 and found a pinkish area around a post that I'd not seen before. I posted a photo, also shown below, and got an explanation of what I was seeing:

The post pictured has been re-soldered which burned off some lacquer and corrosion has developed.
This caused me to investigate corrosion and what I might be able to do myself. In the course of that, I read about "red rot", which could be very bad indeed.

So, I looked at my YTS-21 again and discovered even more on the bell and inside the bell (see photos). This all seems to have happened suddenly. Although this was already a cosmetically poor student rental sax when I bought it 13 years ago, I have taken very good care of it. It gets cleaned and wiped down every time I play it. I don't believe this corrosion was there last month, but perhaps I'm just becoming feeble minded.

Anyway: this truly is red rot, isn't it? There's a lot of it that I'm not showing here. What can be done and what are the costs?
 

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what you've got is only a very mild onset of extremely superficial red rot, even worse than that wouldn't worry my , red rot almost never goes deep,

You could simply remove it if it bothers you but it won't necessarily spread deep.

Another possibility is that these are the remnants of droplets collected on the horn before it was lacquered

Red rot sounds a lot worse than it really is. The metal alloy loses zinc and reveals the copper component.

https://www.silverandbrassmusic.com/damaged-lacquer--red-rot-dezincification.html


In extreme cases the corrosion of a lacquered or silver plated instrument can develop into a condition known to instrumentalists as "Red Rot". This occurs when concentrated spots of corrosion appear on the horn, and through a process called "dezincification" bright pinkish-red spots appear to bloom beneath the lacquer or silver plate. This is usually accompanied by a raised spot in the center, either white or greenish in color. This process is caused because under the right conditions, the zinc in the brass will oxidise and leach out of the metal, leaving behind pure copper. The raised white bump in the middle is zinc oxide, and the bright pink blemish on the horn is the copper that is left behind. When this occurs the structural integrity of the metal is compromised. The pure copper metal that remains is full of holes where the zinc used to be, and it is left in a weakened state. Horns with an advanced case of this will develop holes, and can crack and even crumble away. If this is caught early then there is only one cure: the horn should have the lacquer removed immediately so that the salts causing the concentrated corrosion can be removed. The horn should then be washed in a very hot bath of concentrated soapy solution, so that the alkali (basic) nature of the soap can neutralize any acids that have built up in the affected areas. The horn can then be left in a raw brass finish, or, if desired, resprayed with a fresh coat of lacquer.

Why does this happen?

Red rot occurs because all metals do not oxidize at the same rate. The speed with which a metal will corrode is known as its "nobility". A metal that is highly noble, such as gold or titanium, will corrode very slowly. A metal with low nobility, such as zinc or steel will corrode more quickly. A metal with very low nobility will also corrode preferentially to another metal if they are in contact with each other. Zinc is one of the least noble of all metals; this is why you can attach a zinc bar to a steel bridge or evaporative cooler to prevent the steel from corroding. Because the zinc has such low nobility, it will corrode first, and until the zinc is completely corroded away the steel will not rust. The same is true if you attach a zinc rod to a copper plate and immerse them in seawater; the copper will not begin to corrode until the zinc has completely rotted away.

Under normal conditions, brass is actually a fairly stable metal, with a relatively high nobility. The copper and zinc are very tightly interwoven, so they both corrode together at a slow rate. Red rot can only occur under special environmental conditions, when, through a process similar to electrolysis, the zinc and copper are ripped apart. When this occurs the zinc, due to its very low nobility, will immediately oxidize, and only pure copper will be left behind.
 

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I really, really, really wish people would STOP calling all reddish oxidation of brass "red rot". "Red rot" has a specific meaning related to trumpet and trombone leadpipes (small diameter, long length, stays wet constantly) where they can pinhole due to corrosion which starts from the inside. By the time the first pinhole is found, there's so much corrosion in the lead pipe it has to be replaced. THIS DOES NOT HAPPEN with saxophones, due to their very large bore and all the open tone holes that mean the interior dries out. (Yes, I suppose every few decades a repair person finds a baritone that's pinholed through in the curl, but I'll bet you it's vanishingly rare.)

What you have there is the reddish oxidation of brass, starting from the outside, on large open surfaces. The only functional significance of its reddish color is that it's not the brown or the green oxidation. All brass objects are subject to all three of these forms of oxidation. In the case of your photos, there are minor defects in the lacquer that have allowed air to reach the brass.

Like all oxidation, eventually the substrate will pit at the location of these oxidation spots. For spots on the outside of a saxophone, pitting big enough to even see will take years if not decades. Actual functional damage from what you are seeing would take centuries.

Just leave it alone. You have NOTHING to be concerned about.
 

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Yes, your horn will probably last no more than another hundred years.
 

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I really, really, really wish people would STOP calling all reddish oxidation of brass "red rot".
I agree. It is simply acne.
 

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Discussion Starter · #10 ·
Thank you, everyone, so much - I was really worried, especially when another website mentioned the structure would be compromised. I started to envision a car's rusty rocker panel from years of salted roads!

This YTS-21 is really a very good saxophone and I've grown fond of it. This is why it's my only sax.

Once again, thank you for the good information and advice on caring for it.
 
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