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Is Stainless Steel finish or Black Oxide on Stainless more durable?

adv.

Q. Does black oxide on fasteners; bolts, nuts, etc. help improve their resistance to galling? Either in 18-8 or 316 stainless.

R BRAUN
- Allentown, Pennsylvania
February 9, 2023

A. Hi R.
I'm not personally aware of any studies on that matter, but black oxide coatings are so thin that I don't think they can have any effect on galling. In fact, I think they'll wear off just about immediately in a wear situation.
Luck & Regards,

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

⇩ Closely related postings, oldest first ⇩

Q. Hello everyone,

I'm wondering if a Black Oxide Finish (on Stainless Steel) is more or less durable then simple Stainless Steel. I don't, unfortunately, know what kinda of Stainless.

I am particularly talking about the new Leatherman Multi-tools with a Black Oxide Finish vs their normal Stainless Steel tools.

Thanks,
Sean

Sean Begley
Electrical Engineer / Gadgeteer - Atlanta, Georgia, USA
April 26, 2010

A. Hi, Sean. I've had several Leatherman tools. Yes, they can rust if left really wet and unattended for months. But in normal use they don't rust, and last just fine. The black color is a matter of which look you like, not corrosion resistance.

Regards,

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

Q. So, to sum up your answer, the Black Oxide finish on the Stainless Steel does not, appreciably, affect the corrosion or wear resistance of the part?

A subtle follow on question, how is the durability of the Black Oxide finish itself compared to un-blackened Stainless?

Thanks,

Sean

Sean Begley
- Atlanta, Georgia, USA

A. Hi, Sean. A black oxide finish on plain steel has virtually zero corrosion resistance. It is usually waxed or oiled, and sometimes lovingly maintained with light oil in some cases such as with hunting rifles. Strip the oil off and the part will often flash rust in hours.

Perhaps one significant reason Glock firearms became so respected is that their Tenifer salt bath nitrided finish was such a huge improvement over black oxide.

Regards,

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

Thank you Ted. That is exactly the kind of information I was looking for.

In this case, it looks to me like adding the Black Oxide finish will (of course) make the part black, but that it causes the part to require more maintenance then with the simple Stainless Steel finish.

Thanks,

Sean

Sean Begley
- Atlanta, Georgia, USA

Q. I'd like to put Stainless Steel (18-8) screws with black oxide on the outside surface of a medical scanner device. In other words, they'll be exposed frequently to cleaning agents and bodily fluids.

Is that a good idea, or should I use screws with more corrosion resistance? My requirements are that the screws need to be black (or at least gray) and that they don't show signs of corrosion (for aesthetic reasons) is this environment over time (10 years).

Victor Dzon
Design Engineer - Cleveland, Ohio, USA
October 11, 2013

A. Victor,
Good question. It's too bad you cannot use Nylon or perhaps a sturdier plastic like PEEK or Ultem, etc. for this project because the proposed materials do not seem optimal. Your idea does probably reduce cost but it seems risky due to two factors. I would consider a change or two such as not using a dark color and not using black oxide coating. If it was my project I would use white, natural, pastel or transparent and substitute a plastic cap screw. Nylon might work but it's pretty weak. One might also consider an interlocking clam-shell (molded plastic) style design or think of a way to eliminate the fastener because that is a trend to reduce fastener count when possible.

Blake Kneedler
Feather Hollow Eng. - Stockton, California

A. The black oxide has no corrosion resistance. However if you apply black anodizing, then the surface will be protected against corrosion in body fluids. This coating is bio-acceptable, applied for surgical instruments, with multiple sterilizations.

adv.
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Anna Berkovich
Russamer Lab

Pittsburgh, Pennsylvania

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