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Red Rot Identification



 
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radman63
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Joined: 30 Jan 2023
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PostPosted: Wed Feb 01, 2023 7:35 am    Post subject: Red Rot Identification Reply with quote

OK. So, I'm trying to learn more about red rot. It seems red rot is "usually" smaller spots of discolored metal that are reddish-pink in color. In many eBay ads, I see large, even patches that are reddish-pink in color, and not the small red dots I've seen on other trumpets.

Look at this listing for example. See the large patches of reddish discoloration? Red rot, or just oxidized brass that can be buffed/polished out? What do you think?

https://www.ebay.com/itm/115681033627
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huntman10
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PostPosted: Wed Feb 01, 2023 8:47 am    Post subject: Reply with quote

That is tarnished brass. The pinkish hue of red rot that might damage a horn is usually under lacquer. Red rot coming from inside shows up as black on silver-plated finish.

Just my speculation of course, but I think the tarnish is chemically similar to the chemical process of red rot, but not focused where it will penetrate and only a few atoms deep. Just polish off the surface of this horn to get shiny brass.
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Ronnman
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PostPosted: Wed Feb 01, 2023 9:16 am    Post subject: Reply with quote

I agree with huntman10. It appears to be brass tarnished over wide areas. Red rot generally shows up as spots and as it advances, dark spots appear in the central part of the spots. See link for a a mix of newer spots and some which are fairly advanced case with the darker centers.
Ron

https://i.pinimg.com/originals/7b/69/67/7b6967e08e97fba9f815fa07139d77f2.jpg
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SilverSpunk
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PostPosted: Wed Feb 01, 2023 9:41 am    Post subject: Reply with quote

Yup, this is just tarnish on the surface of the brass, you can see the same reddish discoloration on the bell as well (red rot wouldn't form from the bell in 99 percent of cases).

Red rot is usually pinkish or reddish pinkish spots and it only really gets bad once you see a blueish hue inside the spots.
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radman63
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PostPosted: Wed Feb 01, 2023 10:50 am    Post subject: Reply with quote

Thanks for the replies. I thought these large areas were not red rot, but I wanted some advice. Maybe I'll buy a trumpet like this and see how well it cleans up.
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radman63
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PostPosted: Fri Feb 10, 2023 4:45 am    Post subject: I bought it Reply with quote

I ended up buying the trumpet I referenced in my original post, so I guess I'll see how well it cleans up!
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Irving
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PostPosted: Fri Feb 10, 2023 6:40 am    Post subject: Reply with quote

It hasn't been mentioned here but red rot usually occurs on the leadpipe and possibly on the tuning crook. It starts from within the horn and eats its way through the brass. The horn you bought looks OK. You can surmise that there isn't any red rot since there are no indications, but when you get the horn look down the leadpipe. If it is smooth like a rifle barrel then it has no red rot. If you can see craters that coincide with brownish spots with a pink center on the outside, then that would be red rot.
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jeirvine
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Joined: 29 Apr 2022
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PostPosted: Fri Feb 10, 2023 7:22 am    Post subject: Reply with quote

So does the difference between red rot and tarnish come down to whether it starts internally or externally? I've had plenty of old horns that had obvious red dots on the outside from either water key spray or other external moisture. Often this can be buffed out, but sometimes the dots go a little deeper and will leave a tiny pit.
My understanding is that red rot results from internal moisture causing the chemical de-zincification of the brass from within. Are the two processes chemically/metallurgically different, or is it just a matter of internal vs. external source?
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yourbrass
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PostPosted: Fri Feb 10, 2023 7:49 am    Post subject: Reply with quote

Irving wrote:
It hasn't been mentioned here but red rot usually occurs on the leadpipe and possibly on the tuning crook. It starts from within the horn and eats its way through the brass. The horn you bought looks OK. You can surmise that there isn't any red rot since there are no indications, but when you get the horn look down the leadpipe. If it is smooth like a rifle barrel then it has no red rot. If you can see craters that coincide with brownish spots with a pink center on the outside, then that would be red rot.


+1

Really advanced rot can be seen on silver plated instruments as bubbles on the outside of the leadpipe or tuning crook. Even so, it can often be cleaned inside and with proper maintenance, it will still last for years.
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