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DIN 50938 Black Oxide Finish

A discussion started in 2001 but continuing through 2017


Q. We need to perform a finish according to DIN 50938 [affil. link to spec at Techstreet] but the spec we received is in German. Almost on top of the page it says in English: "Alkaline Blackening (Black finishing) of Iron materials".

The german title is: "Brunieren von Gegenstandan"

We think it is black oxide since its an alkaline blackening operation, but somewhere in the spec there is a table that mentions a requirement of 5.5 g/m2

Is our assumption correct? Do you know what the spec calls for?

Thank you very much for your help,

Enrique Segovia
- Monterrey, Mexico

A. Hi Enrique. The good news is that the spec is available in both German and English versions. Your command of English seems excellent, so I'd suggest just getting an English copy. Good luck!


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Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


Q. We have got a component which specifies the following: Surface Finish: Alkaline Black to DIN 50938 [affil. link to spec at Techstreet] Does this mean Black oxidizing or phosphatizing?

Sudhir Aptekar
- Belgaum, Karnataka, India


A. Hi Sudhir. It's a black oxide finish. But don't even think about offering to process to a spec without having the spec on hand, because you're not offering to do "a black oxide finish", you're offering to "Black Oxide per DIN 50938" -- that's a very big difference :-)

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Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Need 72 Hrs. salt spray resistance after black oxidation

January 28, 2008

Q. Hi,
One of our components requires 72 hrs. NSS results after black oxidation.
Specification is DIN 50938 [affil. link to spec at Techstreet] C, and suggests a three stage oxidation process in hot alkaline bath with temperature difference of 5-10 °C at each stage in increasing stages from first bath to third one.
Is anybody familiar with the above process and with the required results of NSS?
Please share the ideas.

Rajendra Pawar
Plating shop owner - Pune, Maharashtra, India

July 14, 2016

Q. My Customer requires Black Oxide coating as per DIN 50938 [affil. link to spec at Techstreet] - Fe/B/T4 and Corrosion protection of 70 hours as per ISO 6270-2 [affil. link to spec at Techstreet]

But as per DIN 50938. The Black Oxide coating mean mass must be 5.5 gms/m2. Please clarify.


lasu mathews
- chennai, Tamilnadu, India

July 2016

A. Hi Mathews. It sounds to me like, in addition to processing to DIN 50938, the parts must also pass a 70 hour humidity test per ISO 6270-2. I do not have DIN 50938 on hand, but you must. Can you tell us if it specifies a humidity or neutral salt spray exposure requirement in addition to the weight requirement?


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finishing.com - Pine Beach, New Jersey

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