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Raised bumps on Duca Di Montefeltro receiver


Hill_Country

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I recently inherited a 12 ga Duca Di Montefeltro shotgun.  I'm just floored by the beauty and feel of this gun, however there are raised bumps on the receiver that I don't see on photos of other similar weapons.  At first, I thought they were part of the engraved scene, but now I don't think so.  They don't appear to be structural defects, but they do detract from the beauty of this gun.  This must be some sort of corrosion, but there is no rust or corrosion anywhere except on the receiver.

Anyone ever seen anything like this?  Anything that can be done about it?

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I think you're right. It looks like corrosion under the finish. Like the paint bubbles where rust is starting on an older car. I would think the only thing you could do is have it refinished, hopefully not destroying the engraving and inlays. Or just ignore it, but it will continue.

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Thanks, not what I wanted to hear, but what I expected.  What baffles me is that the bumps are solid and usually when plating starts flaking off the bubble is soft and easily broken.  These bumps are solid.  I've spent about two weeks in the aerospace maintenance business and thought I'd seen every possible type of corrosion, but this is a new one on me.  I'm also surprised that only the receiver has any damage - usually the blueing is the first to show mishandling.

I can't believe this is the first case of this cancer and wonder if I can expect any help from the factory.  I've emailed customer service, but have yet to hear back from them.

BTW, I'm embarrassed by the filth that these photos show.  My guns may not be spotless, but they do get cleaned regularly and after every range session.  In this case I've deliberately not cleaned up this gun until I find out what I'm dealing with.  

 

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On 12/10/2021 at 6:43 PM, remarkable said:

What is the build date on the gun?  How was it stored?

I talked to CS this morning and they say it is a 2009 manufacture so no warranty help.  The lady I spoke with said they had never seen anything like this, but she didn't impress me with her technical knowledge.  She did specify that their Maryland location is their only US repair station and they don't do any plating or blueing work.

I have zero information on the storage conditions, but I did a little more investigation while cleaning this thing up.  Got out the big magnifier and opened up a couple of these bumps and it is obviously corrosion of the aluminum under the nickel plating.  Google says, "Nickel is cathodic to aluminum and a breach in the plating will lead to rapid corrosion of the aluminum."  That's obviously the case here.  The question is what caused the breach in the plating.  There's no obvious injury to the plating and if there were an environmental problem with the storage I would expect rust on the blued areas before the receiver would corrode.  From the pattern of the corrosion on both sides and top of the receiver, galvanic corrosion doesn't seem likely, either.

I think my next step will be to visit a couple of the high end gunsmiths in the area - I'm not far from the National Shooting Sports Complex - and see if they can recommend a plating shop.  I understand that electroless nickel plating on aluminum is nothing for amateurs.

 

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I appreciate the ideas.  I don't think ignoring it is an option as the corrosion is going to continue so the existing plating has to be stripped.  Cerakote is a good option, but either Cerakote or re-plating will require me to completely disassemble the receiver, which I'll have to do to strip the existing plating, anyway.  I guess it will depend on what the substrate looks like when we get the plating off.  If it is badly pitted, Cerakote might be the way to go.  (Maybe bondo the pitts. <G>)

I'd still like to know what caused this and I can't believe this is the first Benelli receiver that has had a corrosion problem.  There must have been a problem with the plating.

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  • 2 weeks later...

I talked to a gunsmith in a really high end shop and he said he's seen this type of corrosion in other brands as well as Benelli.  He believes it is strictly due to poor surface prep by the manufacturer. 

Next stop was a plating shop.  He confirmed that it is corrosion of the aluminum receiver under electroless nickel plating.  Said while chemical stripping EN is not that difficult, the problem in this case is doing it without damaging the much softer aluminum receiver and he wasn't set up for that as it requires kind of a reverse electrolytic plating process.

So I went to a plating shop that specializes in aerospace parts and has an impressive list of certifications.  As it turns out, one of the owners was a former professional skeetshooter who was well acquainted with shotguns and the corrosion problem.  He said his shop could do the work, but it would be expensive - probably half the value of the gun just to strip the plating.  By the time I was finished cleaning, polishing and replating or Ceracoating I'd have more in the repair than the value of the gun even if I did all the disassembly and reassembly.  They were also unwilling to work on a gun part.

I spent some time with a big magnifier and popped a couple of the larger bubbles.  Under the plating is grey oxidation consistent with aluminum.  The aluminum receiver does not appear to be pitted and cleans up pretty well with just a bit of Flitz on a patch.  The problem is that even if I popped all the bubbles - which would be very difficult - the edge of the remaining plating would show through Ceracoat.  I don't know of any way to clean it mechanically as bead blasting or wire brushing the very hard nickel plating would destroy the aluminum underneath.

Benelli customer service tells me this gun was manufactured in 2009 and had a five year warranty.  They claim to have never seen a problem like this, can't offer any warranty assistance nor are they willing to try to repair it.

Any ideas would be appreciated, but it looks like I'm out of ideas, out of luck and I'd better get used to an ugly gun.  Hope this information helps someone else.

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1 hour ago, Hill_Country said:

I talked to a gunsmith in a really high end shop and he said he's seen this type of corrosion in other brands as well as Benelli.  He believes it is strictly due to poor surface prep by the manufacturer. 

Next stop was a plating shop.  He confirmed that it is corrosion of the aluminum receiver under electroless nickel plating.  Said while chemical stripping EN is not that difficult, the problem in this case is doing it without damaging the much softer aluminum receiver and he wasn't set up for that as it requires kind of a reverse electrolytic plating process.

So I went to a plating shop that specializes in aerospace parts and has an impressive list of certifications.  As it turns out, one of the owners was a former professional skeetshooter who was well acquainted with shotguns and the corrosion problem.  He said his shop could do the work, but it would be expensive - probably half the value of the gun just to strip the plating.  By the time I was finished cleaning, polishing and replating or Ceracoating I'd have more in the repair than the value of the gun even if I did all the disassembly and reassembly.  They were also unwilling to work on a gun part.

I spent some time with a big magnifier and popped a couple of the larger bubbles.  Under the plating is grey oxidation consistent with aluminum.  The aluminum receiver does not appear to be pitted and cleans up pretty well with just a bit of Flitz on a patch.  The problem is that even if I popped all the bubbles - which would be very difficult - the edge of the remaining plating would show through Ceracoat.  I don't know of any way to clean it mechanically as bead blasting or wire brushing the very hard nickel plating would destroy the aluminum underneath.

Benelli customer service tells me this gun was manufactured in 2009 and had a five year warranty.  They claim to have never seen a problem like this, can't offer any warranty assistance nor are they willing to try to repair it.

Any ideas would be appreciated, but it looks like I'm out of ideas, out of luck and I'd better get used to an ugly gun.  Hope this information helps someone else.

Beauty is in the eye of the beholder mi amigo. As I said, it's part of the history of the gun.

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Personally I would leave that finish alone. Any refinishing attempt is going to ruin that engraving. It would wreck the gold inlay as well. Bead blasting that finish off is going to remove detail from the engraving work if not ruin it completely.

Around 2015-2016, I had a factory engraved, nickel plated 1873 that was made around 1876. I had a letter generated from the Winchester museum in Cody Wyoming that documented that it was in fact engraved and plated by the factory. It had spent god knows how long in Europe before I exported it back to the US. The nickel finish was in rougher condition than what you have there. If you handled the surfaces, you'd have nickel flake off here and there. Even being as rough as it was, a collector still wanted it bad enough to pay around 15k for it. Had it been messed with or refinished at some point, the value would have tanked.

The corrosion and wear has its own appeal for these type of rifles. I'd hate to see what appears to be actual hand engraving ruined in a refinishing attempt. Sometimes the engraving work is the cause of the contaminants. Imagine some guy with his greasy hands resting on the bare receiver for 6-10 hours as they etch the scenes. If those skin oils aren't flushed off of the surface correctly when the nickel finish is done, this cancer type scabbing might develop.

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1 hour ago, StrangerDanger said:

Personally I would leave that finish alone. Any refinishing attempt is going to ruin that engraving. It would wreck the gold inlay as well. Bead blasting that finish off is going to remove detail from the engraving work if not ruin it completely.

Around 2015-2016, I had a factory engraved, nickel plated 1873 that was made around 1876. I had a letter generated from the Winchester museum in Cody Wyoming that documented that it was in fact engraved and plated by the factory. It had spent god knows how long in Europe before I exported it back to the US. The nickel finish was in rougher condition than what you have there. If you handled the surfaces, you'd have nickel flake off here and there. Even being as rough as it was, a collector still wanted it bad enough to pay around 15k for it. Had it been messed with or refinished at some point, the value would have tanked.

The corrosion and wear has its own appeal for these type of rifles. I'd hate to see what appears to be actual hand engraving ruined in a refinishing attempt. Sometimes the engraving work is the cause of the contaminants. Imagine some guy with his greasy hands resting on the bare receiver for 6-10 hours as they etch the scenes. If those skin oils aren't flushed off of the surface correctly when the nickel finish is done, this cancer type scabbing might develop.

Yes, refinishing - done improperly - would ruin the engraving.  It would also likely ruin the receiver.  That's what I'm trying to avoid.  Any attempt to *mechanically* remove the (very hard) plating will compromise the much softer aluminum substrate.  With that said, the plating can be removed non-mechanically by essentially reversing the plating process.  The problem is that the process is not economically feasible IF I could find a shop that would take on the job.

Also, FWIW, the gold is not an inlay and appears to be a sintered bronze "paint" applied over the plating.  Not difficult to repair, though.

I agree that refinishing this gun would significantly devalue it if it were a collectable, but its just an otherwise fine firearm with a bad case of acne.  While its probably still a fine shooter, I expect the open market value is half or less of what it would bring without the corrosion.

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