M Body Shell Material and Corrosion

[chris_chen]

I've never seen this asked before:

 

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What metal are the body shells made of?

 

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I want to say aluminium, as it wears to silver where the bottom plate is removed 100's of times. It could be magnesium too, I guess.

 

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I took a graduate level corrosion course years back, but don't use it much, hence the ignorance. If the body shell material, as a result of normal wear or maintenance, comes into metal-to-metal contact with zinc or brass top and/or plates how much of a galvanic current is going to be generated? And if this area gets moist from the environment, which will corrode faster (sacrificial anode).

[chris_chen]

Sorry, I tried hitting the stop button to make corrections; I see

they went through anyway. Please Delete Tony; it lokks awful.

[andrew n.bra hrefhttp]

See the various topics in the nemeng.com/leica faq.<P>

 

Generally speaking, the latter M4-P's and all production run M6s are

made from <B>Zinc Alloy</B>. The M3, M2, M4-2, v.early M4-Ps, and M7s

are made from <B>brass</B>.

[chris_chen]

Andrew,

 

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I love your site. But the question is about the body shell, not the

top or bottom plate.

[giles_poilu]

All the M body shells have been made the same way, a hard-drawn

aluminium alloy shell encasing a die-cast chassis. Apart from the

late M4-P's and all M6's (excluding M6J and painted M6 specials) all

top plates were brass. ALL M baseplates are brass. The M7 has seen

the return to brass top plates.

[giles_poilu]

Chris, for more on this subject try and get hold of a copy of "A

History of the 35mm Still Camera" by Roger Hicks, it's a fascinating

book and goes into great detail on the evolution and construction of

the Leica amongst others.

 

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Some of the most gratifying text is the comparison of materials used,

typically:

 

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"Let us now look at the materials and connectors used for flash

mechanisms. Although some of the lesser makes got away with copper

and brass, almost all the better ones used some sort of precious

metal plating, usually gold, to guard against oxidation of contacts.

Leitz, of course , went one better and used solid platinum - iridium

(!) in the M2 and possibly M3, solid 80 per cent gold elswhere."

 

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Judging by the M4-P sync. problems maybe they forgot about this then!

[andrew n.bra hrefhttp]

Good point - because you spoke of external wear I had mistakenly

assumed you meant the outer casing, not the interior frame.<P>

 

The interior frame is alumninium alloy. What type, I don't know.

Don't know the likelihood of the frame corroding either (although I

suspect it wouldn't as it is too protected with clading or paint).

[andy_piper2]

Actually - I asked a Leica rep today and SHE said the main casing (the

heavy flattened metal 'tube" that's covered with vulcanite/vinyl and

holds the shutter box and film inside it) is steel.

 

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FWIW.

[Rob F.]

So, Chris, what's the corrosion potential . . .

 

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. . . if it's aluminum

 

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. . . or if it's steel.

 

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No corrosion noted on my M2 after 40 years (brass top plate).