M6 Top Plate = strange marks
Old 06-29-2017   #1
elmarman
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M6 Top Plate = strange marks

I have some strange black marks on my 1986 M6 top plate -- they are nor 'dirt' as you can see around 'hot shoe' that I need to clean off with cotton bud -- they will not clean off. It looks as if the metal is going rotten ! Any Ideas ?
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File Type: jpg Top Plate Marks.jpg (20.0 KB, 161 views)
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Old 06-29-2017   #2
sevo
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Salt water spray corrosion? Or a flaw in the plating process? I've seen similar damage due to either.
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Old 06-29-2017   #3
Stelios
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Mine has similar marks. I thought it was normal camera wear.
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Old 06-29-2017   #4
Rob-F
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I think it may be a zinc top plate, rather than brass. Problems have been reported both with paint and with plating over the zinc top plates; they went back to brass for that reason, and because zinc tends to crack under stress, whereas brass only dents.
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Old 06-29-2017   #5
Dez
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Chrome plating can be porous, especially if process quality is a bit off the mark on a particular batch. It does look as if you have a zinc top plate and it is corroding, as zinc is fairly reactive. Not a great move going to zinc moldings for Leica top plates given the price of the cameras.

Chrome quality can be quite variable. Contax chrome was a bit iffy in the just-prewar years, and interestingly, the early FSU Kiev copies has considerably better plating. Heresy, but true.

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Old 06-30-2017   #6
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Thanks for all your 'expert ' views ! I thought I would get some answers here!
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Old 06-30-2017   #7
jarski
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Quote:
Originally Posted by Rob-F View Post
...because zinc tends to crack under stress, whereas brass only dents.
I don't see any cracks in the picture, nor understand how that part of camera would be under a stress.
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Old 06-30-2017   #8
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Quote:
Originally Posted by elmarman View Post
Thanks for all your 'expert ' views ! I thought I would get some answers here!
Ha! We're all experts, but since this is the internet that makes us internet experts. And since I'm sitting in an armchair I suppose I'm an armchair internet expert.

The only thing better than a free opinion is lots of them. Welcome to the internet.

FYI your camera is suffering from a rare disease among Leica's, called Overuseitis. It generally happens after a camera is used as intended, and the main symptom is called wear and tear. There is no cure, only a preventative, called Shelfqueenium.

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Old 06-30-2017   #9
Richard G
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"Bubbling" is what's usually reported. This looks different. Here's Tom Abrahamsson on some aspects of the Zinc used in M6's; http://nemeng.com/leica/042b.shtml
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Old 06-30-2017   #10
mcfingon
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Slightly off-topic, but related: could the zinc top plate on my 1986 M6 make the shutter sound better damped? It's the quietest of the Leicas I have owned (M2, M3, III and IIIf).
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Old 06-30-2017   #11
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Quote:
Originally Posted by jarski View Post
I don't see any cracks in the picture, nor understand how that part of camera would be under a stress.
It's not that there is a crack in this specific camera. They switched to zinc for a while in the hope that the top plate would be less likely to be dented from impact. But that switch merely traded the tendency to dent for a tendency to crack under stress. So that, plus the cosmetic difficulties, added to, I imagine, objections from the Leica community over the change away from the more traditional brass, have evidently moved Leica to return to brass. Cracking is merely one of the things that go wrong with zinc. I don't mean that it was the problem in this case.

It seems to be okay with us for a Leica to become brassed from use; and not okay for one to become "zinked."
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Old 06-30-2017   #12
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I have an early production black M6 marked "Wetzlar" on top similar to the one pictured by the OP, just a slightly later serial number, and it has quite a bit of the bubbling going on. Otherwise, fine. Recently had the rangefinder converted to the no flare MP-type by Youxin.
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Old 06-30-2017   #13
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My old M6 showed similar wear, but only in high wear places. See here:
http://www.rangefinderforum.com/foru...d.php?t=146044

I can only suspect it was been rubbed in the bag or artificially somehow. It is not the Zinc corrosion problem, it is how Black Chrome wears.
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Old 07-02-2017   #14
GarageBoy
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Yeah, potmetal/zanmak/zinc alloy wasn't a great move - you see that on brass cameras too, but it's usually just some verdigris, instead of bubbling
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