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Thanks for that, Juan.

Our conversation regarding pitting corrosion certainly brought up many thoughts. For one, we have the evidence that in the worst case of aqueous environment - the unprotected interior of the horn - we don't witness pitting corrosion. What I had previously failed to consider is the contribution of environment to the galvanic cell(s) on the exterior surface of the horn. We certainly witness enhanced pitting on horns near coastal regions - hence my professed stance of needing to protect the horn against further corrosion by maintaining some finish.

For those unfamiliar with galvanic pitting corrosion, here it is in a nutshell: A galvanic cell is one in which a potential energy drives the removal of metallic ions from the surface of a metal with the electronic balance provided via a conductive aqueous path. The classic case is a ship's hull made of steel sitting in sea water. The corrosion of the hull can be reduced by using a sacrificial anode with a greater differential potential - hence the anode corrodes in preference to the steel hull.

Pitting corrosion occurs when the active area of the galvanic cell is reduced and the local flux of ionic exchange is enhanced - an example is when a storage tank with an internal coating loses pinpoint coverage of the base metal. In the case of a saxophone, this occurs when the lacquer breaks down on the microscopic level and allows tunneling to the base metal. The resultant corrosion cell has enhanced activity and leads to accelerated corrosion in a confined area >> pitting that drills into the body of the horn.

That leaves us pondering the answer to the problem. I see three possibilities that I present in no particular order. The first is a more impermeable and robust finish ala the epoxy finishes that have become popular. The second is the unlacquered finish - WITH THE CAVEAT that it will still be vunerable to corrosion and that local galvanic pitting corrosion may occur, for instance, at crevices such as body/post joints, threaded regions, and spring mounts. The third option is heavy plating - to date we have seen nickel, silver, and gold.

Comments???
 

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I've lived most of my life in coastal environments (cities by the sea and by big rivers) and the most stable finish is no finish at all.
What's your experience with pitting on plated horns?
 

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Thanks for your answer. Very interesting. Something new to me, so I have a question in this regard.
My SBA is an original lacquer and in pristine condition, but has a corrosion around low Eb keycup. I was told by a tech not to worry about it, as the corrosion itself is like a "barrier" and it's protecting the brass underneath.
I won't commit an opinion as to whether to delacquer or not.

Regarding the corrosion acting as a barrier: That is only true in the case of a limited number of oxides, silver being one case, where the oxide is conductive and does not spall. I cite silver here because, in my former life as a shipboard electrician, I worked on high current breakers with silver contacts. The procedure for refurbishing silver contacts is to leave them alone rather than try to remove the oxide. Of course, on a plated instrument, once the plating is penetrated, you are back to the issue of exposed metals of dissimilar potentials with a shared conductive path in an aqueous environment (bonus points to the reader recognizing the definition of a galvanic cell).

Brass and copper have several oxide states - most of them either porous or, worse, compressive in nature such that they tend to spall off in chunks leaving fresh material exposed e.g. the classic red rot.

I believe that Juan tends to go a step further with his own horns and uses a protective wax applied periodically to slow any general corrosion due to sea shore environments.
 

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My pads are really good, like new with 95% life in it.... I will have this SBA forever, but to strip such original horn would be very hard for me. Is there anything else I can do about that spot?
Juan - What of using wax over that area to slow the process?
 

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Z - Do you use any wax or polish?
 

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Funny you mention that, I use the same polish on my cars and lacquered saxes (and guitars, for that matter):

Meguiars Cleaner/Polish. Highly recommended for cleaning and protecting lacquer finishes - in the boutique guitar community, many builders use this line of products on expensive guitars.
 

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I reference the interested reader to "Principles and Prevention of Corrosion" by Denny Jones.

Foremost, let's recognize that there exist many forms of corrosion. I agree, Oric, that this is not the case of dissimilar metals such as in Stephan Howard's example. Differential electric potentials may also be established just by a gradient in chemical concentration. Regardless, once a cell is established, one needs to identify its characteristics and determine how to either interrupt the reaction or diffuse it.

Although I have a knee-jerk response to even seeing most threads about delacquering, I have to consider Juan's hypothesis as having some credence - especially in the light of having played so many vintage horns over the years with pitted lacquer yet pristine bores. Now, whether those bores remain so smooth is a testament to the fact that there are no posts, plates, joints or otherwise, I just don't know.

(FWIW and OBTW, I use a Shove-it swab and periodically treat it with lemon Pledge so the bore of my horns is smoooooth and lovely. No funk, no stink.)
 

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I think this might be a great guess!!! It looks like corrosion goes from spot under removabell ring, right in the middle! However only one thing that may not go with this theory is that corrosion goes only to the left side of the tone hole, and right side is clean and not affected. If it would be from a leak...
Looks to me like it's the result of condensation accumulating when the horn is put in its case and the case is put away. That's why I store my horns on end - any accumulation of moisture collects in the bottom of the bell rather than the Eb key. Ever notice a lot of moisture/staining on that pad? Sticky pad? If not you, then the previous owner.
 

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... and dry the bore before you put the horn away. ... and apply the occasional coat of Meguiars.

That is a sweet lookin' horn. Enjoy.
 

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While I always swab out my tenor, alto, and sop, ever tried to do that with a bari? Doesn't seem to suffer from the lack of attention, though I do have sort of a snake-like affair I use to dry out the upper crook before putting it away.
Chances are that the majority of the wet stuff is trapped in the crook.

My horns get wet when I play. I used to get the occasional sticky low Eb pad from accumulation just as seen on Z's tenor. That's when I learned to better pay attention to why the juice was gathering there.
 

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so wy not make stainless steel saxes
Formability, mass, cost, high flow stress necessitating different manufacturing methods...
 

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i still want a stainless steel sax. maybe passivated. if i recollect right, pitting of stainless is really only in salt environments.

I wonder about an aluminum sax that is anodized. they are great even in salt environs. form it all anealed then heat treat to get it good and hard. it will be lighter than brass ( about 1/3 the weight) and more corossion resistant. hard anodize can be done in colors too. its not as shiny though.
Thanks for the derail. How 'bout starting a thread on alternate materials?
 

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What do you mean? Flute should be only good for classical, but when it comes to jazz doesn't matter? :)

How's that for derail DrG?
Z, you should know my feelings on this by now...

Tenor - It's all that matters.
 

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- or longer lasting saxophones.
50+ years isn't enough???

We don't need to make the saxophone idiot proof, we just need to educate people to treat them appropriately.

I, for one, am weary of "built like a tank" being perceived as a favorable thing. How 'bout "built like a musical instrument"?
 
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