What is Black Chrome?

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hlockwood

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In my years as a (now retired) materials scientist, I never came across the term "black chrome." But now, as one who has fallen (and still falling) into the rabbit hole of Leica Land with the purchase of a black chrome M7, I'd like to know, what is black chrome?

Harry
 
hlockwood said:
In my years as a (now retired) materials scientist, I never came across the term "black chrome." But now, as one who has fallen (and still falling) into the rabbit hole of Leica Land with the purchase of a black chrome M7, I'd like to know, what is black chrome?

Harry
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Added note: There is an adjacent post here that points to http://nemeng.com/leica/042b.shtml where there is some helpful information. "Chrome" probably means chromium plating, leaving open the question, for me, of how it gets to be black. I guess my M7 is "blackened chromium-plated brass."

Harry
 
Dear Harry,

Whatever it is, it's 'orrible. It certainly isn't enamel. It's a bit like anodizing, and a bit like chrome plating, and it wears very badly leaving bright shiny metal underneath. At least my M4-P did, though I understand it's been improved since -- it couldn't get worse. And it's on zinc, too...

Give me satin chrome or (better still) black paint, every time.

Cheers,

R.
 
I don't know what it is either but it wears better than black paint but not as well as silver chrome. Some people like the way black paint wears down to the brass beneath. The only very worn black chrome Leicas I've seen only looked like shades of grey. Not at all ugly to my eyes but some people think this is an example of a "beautiful" Leica:

http://members.lycos.co.uk/JemK/Pic-A-Week/marshall.htm

Personally, I just use them as long as they work without really caring how good or bad they look on the surface.
 
Chromium is a silver coloured metal, normally electroplated onto a subsrate which in most case has already been plated with nickel. Black chromium is deposited from a specially formulated solution contaning chromic acid and generally acetic acid plus other proprietary chemicals. The black chromium coating is an impure from of the metal, containing some compounds of chromium as well as the metal. As such it is generally less durable and resistant to abrasion than pure chromium which is a very hard metal. The chromium covering for decorative purposes is generally less than a micron thick.

Jeff
 
Gumby said:
Is what you describe the same, or different, from a Parkerize (phosphated) finish?
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I don't think that Parkerizing is the same process as used for black chrome. Parkerizing cannot be used on stainless steel where as black chrome process can. That should explain the use of black chrome in the firearms industry as stainless steel firearms are now popular.

Bob
 
delander said:
Chromium is a silver coloured metal, normally electroplated onto a subsrate which in most case has already been plated with nickel. Black chromium is deposited from a specially formulated solution contaning chromic acid and generally acetic acid plus other proprietary chemicals. The black chromium coating is an impure from of the metal, containing some compounds of chromium as well as the metal. As such it is generally less durable and resistant to abrasion than pure chromium which is a very hard metal. The chromium covering for decorative purposes is generally less than a micron thick.

Jeff
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Terrific, Jeff. Thanks.

Harry
 
Well, you won't find it on either Bigfoot or Bubba, but I have seen what's beneath the Black Chrome on the M5. It's yellow-ish. Brass I assume. Yes, a well used Black Chrome M5 shows brassing not unlike what's underneath the black paint on my Canon EF body.
 
Roger Hicks said:
...Whatever it is, it's 'orrible. It certainly isn't enamel. It's a bit like anodizing, and a bit like chrome plating, and it wears very badly leaving bright shiny metal underneath. At least my M4-P did, though I understand it's been improved since -- it couldn't get worse. And it's on zinc, too...Cheers,

R.
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The current black chrome is much better I think, and my first M7 is just starting to 'break-in' with some 'glow' showing through on the corners. I like the way the black chrome ages at least on the brass bodies. Looks more like a tool than a camera.

venchka said:
Well, you won't find it on either Bigfoot or Bubba, but I have seen what's beneath the Black Chrome on the M5. It's yellow-ish. Brass I assume. Yes, a well used Black Chrome M5 shows brassing not unlike what's underneath the black paint on my Canon EF body.
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Yep, a yellow-ish glow. My M5 is black, but I've yet to get any glow on it. Yet.
 
The black chrome that leica uses is called Eloxal. It is a chromium salt and it is a proprietary process , held by Leica. You can buy the stuff, at a cost, and do it yourself. However, as it involves hydrochoric acid and cyanide + other very toxic chemicals. it is not recommended for "home" experiments!
The surface has to be covered first with a copper layer and the a nickel "sealer" and after that you can "strike" the black chrome. The surface can be glossy, semi-matte and dull matte. It all depends on the treatment of the underlaying surface. If you polish the nickel surface to a high gloss finish, the black chrome will come out glossy black.

Anodizing is a different process. This is a electro plating process that works with alloys. The difference is that black chrome is deposited on the surface, while anodizing is a coloring of the surface layer. The advantage is that anodizing does not change the dimensions of the part, Black Chrome tends to build up around the edges and has to be either sealed off or ground off! You cannot "anodize" brass unlss you strike an alloy based surface on to it (very tricky!).
Anodizing also offers an array of colors - though precise colors depends to a great extent on which composite alloy you are using.
From a practical view, anodizing is easier to deal with (and much more economical) and you can change surface structure and "harden" the surface.
Years ago I made a series of winder parts that used a "hard anodizing" process. I was not sure of the long time wear of the slider in the winder and this process is similar to what is used in radial aircraft engine cylinder bores! A bit of an overkill as even using regular alloy (2024) nobody has managed to wear out a slider yet!
Only thing that will probably outlast the hard anodized sliders are the siainless steel ones. It was a special order for some Nat'l Geo shooters and these sliders took 4-5 hours to machine! Heavy too!
 
Tom A said:
The black chrome that leica uses is called Eloxal....
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Thank you Tom. Very clear explanation.

I just wonder why black paint M4 in earlier serial numbers came before black chrome introduced after M5 production (I may be wrong, did M4 black chrome exist before M5??? :confused: ).

It seems that M4 chrome needs more complicated procedure then I thought black chrome M4 must be produced before black paint when Leitz was financially fine...

I (again) may be totally wrong; black paint may need more delicate procedure...:p
 
The "slider" is the arm that connects the lever to the drivebelt in the Rapidwinder. My terminology on my own products is rather haphazard. Most of it ws created as I was developing the winder and it took awhile to make it comprehensible to my the guy who programs the CNC machines! There were "thingimajiggis" and "gizmos" galore. In the end I settled for descriptive terms for the parts!
As for the Black Chrome versus the Black Paint. Leica had a long history of doing black paint cameras. In one of Leicas internal publications there is a wonderful shot of the "paint" division (circa 1930). The painter is holding the part with a small wooden dowel and spraying black laquer on it, window is open to draw out the toxic fumes and behind him is the supervisor, pipe in his mouth!
The black chrome was purportedly developed at Midland and the first camera with this finish was the Midland marked M4 and later there was a series of Wetzlar M4's with the same finish. About 2500 Midland M4's and 2000 of the Wetzlar ones. These were the last of the M4's . The black paint M4 came quite quickly after the 1967 introduction of this model. The pro's wanted a more discreet camera (Ed van Den Elsken was one of the guys who wanted one in 1967).
The first Leicaflex SL's came in chrome,black paint and then in black chrome too. I have a SL Mot in black paint and that is evidently a rare item, "a collectible" - or it would be if it was mint. It is not!
Dont worry too much about the finish, when in doubt put black tape on it if you want to preserve it. I did have an original M3 Double Stroke black paint (it was a special order for the Swedish Press Union of 51 cameras, MP drivesystem, but no Leicavit). The previous owner had carefully taped the corners to avoid strap marks and also put some tape on the top to prevent meter marks, or maybe just to cover up the Leica logo. problem was that the paint on the rest of the top was worn off and there were these black squares from the tape and the rest was all beaten up brass. Jim Lager saw the camera and said "Ok, now I know what a
"Ugly - -" looks like". Well. I paid the princely sum of $80 for it and used it for many years without the tape and managed to even out the wear. Traded it for a new M6 and a 50f2 Summicron in the early 90's.
 
Tom A said:
...The previous owner had carefully taped the corners to avoid strap marks and also put some tape on the top to prevent meter marks, or maybe just to cover up the Leica logo. problem was that the paint on the rest of the top was worn off and there were these black squares from the tape and the rest was all beaten up brass...
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I think you just described Elliot Erwitts camera Tom.
http://rangefinderforum.com/forums/showthread.php?p=692368#post692368
 
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