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lacquer induced pit corrosion on brass

17K views 79 replies 14 participants last post by  GFC12 
#1 ·
Here's an album: https://picasaweb.google.com/103001...DueToLacquerWear?authkey=Gv1sRgCPmNvZnV8uyOKQ

this is a one owner original lacquer horn. I'd say that the original lacquer coverage was better than 90%. Always taken care of, pampered horn.

You can see after delacquering, the "highs" and the "lows" where it was respectively lacquered and where the lacquer wore off/flaked

I have seen less material removal on heavy buffed relacquers than on the places that became unprotected on this horn. Let alone, a careful relacquer done to protect not to bring up to showroom quality again.

But IMHO the best option is to delacquer and leave it bare brass. No bare brass horn loses overtime the amount of material a lacquered horn loses (that's if you're not constantly polishing it up to have a shiny horn)
 
#2 ·
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???
 
#3 ·
So, if I get it right, brass under lacquer was preserved much better than bare brass parts? Right? Therefore lacquered parts are "higher" and bare brass parts were "eaten". So if brass becomes unprotected without lacquer, why then you need to strip the horn to preserve it? Isn't it better to just spot lacquer those bare brass parts to preserve it? I'm kinda lost here :)
 
#4 ·
no you got it partially right.

What happens is that when 2 different electronic potential parts are on the same surface pitting occurs. I you have 100% lacquer there's wear on the lacquer. But if you have an open pore on the protective coating, that part on the substrate gets destructively eaten way faster than bare subtrate exposed to the elements and not buffed.

I've lived most of my life in coastal enviroments (cities by the sea and by big rivers) and the most stable finish is no finish at all.
 
#14 ·
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.
 
#17 ·
It's a curious thing to see such deep corrosion. Where I've seen it the player has been acidic i.e their sweat is more corrosive thatn usual and you can see where their hands have been in contact.
Where I've encountered galvanic corrosion before was Stephen Howard talking about Martin toneholes potentially falling off. The description there was of two different metals connected with mildly acidic solution - a mild current flows for galvanic corrosion to occur.
In the example of the lacquered saxophone I'm not sure you are going to have the conditions in the places shown for galvanic corrosion to occur.
The way to solve galvanic corrosion is to prevent a current and/ or to shield the the metal by coating with plastic of epoxy. As most modern lacquers are epoxy-based it would seem to be ideal for preventing galvanic corrosion.

So, in my opinion (and I'm no expert), either this isn't galvanic corrosion or the advice to delacquer would seem to be wrong.
 
#19 ·
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.)
 
#38 ·
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.
I really question whether a cell is established in this case. You'd have to have moisture on the right parts of the instrument in the right kind of mix to get a cell. It seems doubtful. I think it's thin grounds to tell people not to lacquer.
I have a mid 60s MkVI in superb condition. No corrosion on lacquered areas of the silver plated keys. As other posts have shown where moisture collects and gets under the lacquer, like on the low Eb, it is common to see corrosion there. You've usually got exposure to damp in corroded areas. It may be galvanic corrosion where the damp is trapped in perhaps, but on the outside of the body where damp can evaporate? It's hardly like a boat sitting in slat water. Something else must be going on.
 
#20 ·
that was going to be my second comment, even the ugliest pitted rotten horn has a smooth bore. The plating inside is also perfect most of the time even when it has flaked and pitting lifts blisters between the substrate and the plating.

the only way to deal with this is either refinishing periodically or just call it a lost battle and use no finish at all (just waxing of the outside of the horn to prevent spots of verdigris due to the occasional saliva drop)
 
#26 ·
Juan, Ive got to dis-agree with you here mate, from a preservation point of view, lacquer wins hands down to no lacquer. Also lacquer is not conductive unlike some of these fancy nickle plating finishes, which are highly conductive

For corrosion to be happening under the lacquer then certain condiitons must exist, you have anode cathode and an electrical circuit, for certain areas to corrode faster than others even with lacquer then you will find mix elements of the brass are in a stronger concentration at these points.

Have you ever seen a car that starts to exhibit a blister under the perfect paint skin, you remove the undamaged paint only to find that there is rust. This is because the mix is slightly compromised at this point in the base metal in comparison to the rest of the panel, when you run a circuit throught the panel, example connect an electrical circuit at the tip of the fender and at the rear of the fender, that area under the paint will start to break down as it gives of electrons to the circuit, when electrons are removed the ferritic metal (car panel) starts to break down to its natural state iron oxide (rust)

The only real way for a sax apart from a complete lacquer coverage would have to be in creating a sacrificial anode that you could fit onto the sax's body
 
#27 ·
In my own warped logic I can see that a plated horn could have problems of it's own because when the plating chips or erodes it leaves an area defined by the edge of the chip where two dis-similar metals like nickel and brass are exposed to the air and potentially an aqueous environment hence triggering their own galvanic reaction. A lacquered horn might get some corrosion where the lacquer is missing but at least lacquer in and of itself wouldn't become a galvanic element in the electrolysis... *** do I know. I enjoyed the thread.
 
#28 ·
Mark Plating ALWAYS has flaws. Pores, scratches, thin edges... the only plating that could be perfect is electroless plating. Then again when buffed to make it shine the plating is going to be thinner on edges. Take a look at your average silverplated keys Buffet clarinets, the keys are heavily pitted chewing thru 3 layers of thick silveplate and a thick layer of copper...

ZJAZZ now that I see the pictuers I'm 100% positive it's the removabell. When you play the horn always to your right even if you think you play "straight up". The removabell is leaking and it's going to were gravity allows. Plus also it could be a bad glue gasket leaking from the tightening of the guard... guess were the torque stress could break that glued joint? yes, towards the side you have pitted on your otherwise flawless horn.

Simso I hear you mate. But lacquer chips, wears, blisters. No lacquer... don't! :bluewink: I have had a gazilion of old horns thru the shop. The thickest sheet metal is on 20's american plated horns, then bare brass horns. Good relacs comes a close second from bare brass. The most destructive pitting I've seen is on late 30's and up to 50's plated selmers, euro lacquer selmers, Martins, and old Yamahas.
 
#29 ·
Mark Plating ALWAYS has flaws. Pores, scratches, thin edges... the only plating that could be perfect is electroless plating. Then again when buffed to make it shine the plating is going to be thinner on edges. Take a look at your average silverplated keys Buffet clarinets, the keys are heavily pitted chewing thru 3 layers of thick silveplate and a thick layer of copper...

(good stuff deleted)

The thickest sheet metal is on 20's american plated horns, then bare brass horns. Good relacs comes a close second from bare brass. The most destructive pitting I've seen is on late 30's and up to 50's plated selmers, euro lacquer selmers, Martins, and old Yamahas.
These two sentences are a little at odds with each other. The thickest metal is on 20's plated horns, but then you also said the worst pitting was on plated horns. Last sentence of the quote says the most destructive is silver SBAs, anything Selmer lacquered in Europe, and any old Yamahahahaha, yet all plated horns have microscopic holes -- unless they don't because they put an inch thick silver plate on it?

Not quite certain there's a rule here to follow. :scratch:
 
#31 ·
Thanks everyone for their info. Thank you Jiciano, I think you are 100% nailed it, yes, I didnt think about holding horn to the right, there for only left side of tone hole affected! Now it makes sense.
What would be your advice to do next? To go to repair shop open removabell and reattach it again? After that leave it as is, and because no additional leak means no additional corrosion? Or clean that corrosion and maybe spot lacquer that part? Also do you think I need to take care of that immediately or it's not such an emergency?
Thank you!
 
#32 ·
I'd have the bell SOLDERED not glued, the corrosion removed and the lacquer touched up since your horn is so nice. I wouldn't say this is an "emergency" but it's certainly nothing to dwell on.
 
#33 ·
... and dry the bore before you put the horn away. ... and apply the occasional coat of Meguiars.

That is a sweet lookin' horn. Enjoy.
 
#35 ·
I have t confess to NEVER dry the bore on the saxophone. I occasionally swab the neck, but don't dry the bore after I play. I dry the neck receiver, wipe away the usual saliva mist or drops around the watering prone keys, but don't dry the bore.
 
#36 ·
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.
 
#37 ·
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.
 
#40 ·
the horn from wich I took this pictures was a PRIME example of preservation on fisrt inspection. I really question wether your horn is "pristine". I'd say that no. This SBA has a cell indeed, in my opinion. But hey... I'm just commenting what I've found over many years of doing, not studying, and you know how when you have an idea you're always convinced you're right. I'm convinced that the best preservation for a player's horn (a horn that is played sometimes! not a display-museum horn) is no lacquer and no plating.
 
#42 ·
I have a MVI Bb bari in all perfect condition except for corrosion marks from the first owner (I'm #2) due to high acidic content in his persperation I would guess.
He can turn a silver flute black quickly and had to have and his MVI alto refinished as a result. Perhaps this is covered in earlier or other places on the site.
Any comments on individual player effect on the lacquer and brass after years of player other than normal dings, etc. from lots of playing.
 
#47 ·
soldering, brazing and forming stainless steel requires way more training, tool expenses and experience than brass. And it pits worse than Brass for the application we're discussing. That's the thing with stainless if it corrodes, it pits really bad
 
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