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Beitrag begonnen von Ted am 27.11.2018 um 19:36:29

Titel: Prewar bolts - black color
Beitrag von Ted am 27.11.2018 um 19:36:29

Hi, my question is about the color of the bolts. A lot of the bolts and nuts in the prewar cars /and maybe in the postwar, too/ were black. But do you know, was it black zinc plating, or black oxidation /like the finish of the guns and pistols/? Thanks!

Titel: Re: Prewar bolts - black color
Beitrag von Baloke am 27.11.2018 um 22:45:06

...talking about "Pre War"

During the forming process of the bolt/nut the the material was oiled (black & dirty oil due to the circulation) to reduce the wear & tear of the tools during their forming. Furthermore became the steel hot due to the forming stress.
The formed parts were than cooled down by throwing them in a oil bath (same oil as above ).
After the cool down the parts were lifted out of the oil tank and let them drain by gravity.
The final product was than called f.e. Bolt M1o, black, oiled.
A lasting corrosion protection was not existing.
When you handled it, you got real black dirty fingers.

Browning Treatment:
For High Quality Bolts & Nuts (like weapons, instruments etc.) the browning process was used to provide a great look and a certain corrosion protection.
During this process the hot bolts & nuts were dipped into the special browning oil. As a result of the interaction during this process a very thin film applied to the metall surface ( approx. 1-2 [ch956]m thick).

Black Galvanized.
It is a today corrosion protection but only for cheap mass products, to my knowledge such fasteners are not accepted longer by the German Automobil industrie due the chome health risk.

Tody widely use.

However, the coating and corrosion protection is a complex area. If you want to go into details, please consult DIN EN ISO 4042 and the numerous interconnected further standards, all available in the www, help yourself further ;)

bis denne/b

Titel: Re: Prewar bolts - black color
Beitrag von Ted am 28.11.2018 um 16:13:05

What a great informative response, thank you so much!  :) So, it is neither plating, nor gun blueing, but just oil darkening from the manufacture process! I thought to send mine for black zinc plating, but then that would be wrong, would be too dark. Then I will do something else - black color by some heating and putting in olive oil. The result is the same like in motor oil, but the effect is achieved at lower temperature, so the bolts won't lose strength. Thank you very much!

Titel: Re: Prewar bolts - black color
Beitrag von Baloke am 28.11.2018 um 17:29:25

...preheating and Olive Oil and/or Rapseed Oil (also called "CANOLA OIL) was yesterday !

Today-use a cold browning process, check this: https://www.waffenpflege-shop.de/brueniermittel-set-von-ballistol.html.

Easy job for small quantities of screws.

bis denne/b

Titel: Re: Prewar bolts - black color
Beitrag von 170ziger am 28.11.2018 um 20:45:43

Hello Ted,
I think it's much easier to put all the screws in a box and then "chrome-black" them to the depositor. Before the black chrome-plating, the parts are cleaned and pickled, there is no rust and the parts look like new again afterwards, black as before.

Greetings, Alfred

Titel: Re: Prewar bolts - black color
Beitrag von Ted am 29.11.2018 um 18:36:19

Yes, that is what I considered from the beginning, for years I use the service of a plating company, they can make black zinc plating. But after asking here, i thought that would be too black?

I may experiment, will send some old bolts and nuts for black zinc plating, also I have good quality gun blueing/browning chemicals, will test these, too. As long as the olive oil "plating" is not that durable, I think I will use either the zinc blackening, or the gun plating.

Thanks for your valuable advises!

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