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Ferritic Nitrocarburizing has red color to it?

Q. Hello! I am looking into an alternate for Chrome plating. I had some 12L14 parts done with Melonite QPQ. I know this is a liquid ferritic nitrocarburizing process and is advertised to have a black finish.

My parts appear to be rusty! I did some reading and saw that the compound layer can contain Fe3O4 and/or Fe2O3. The Fe2O3 is the red rusty iron, and I assume this is where my discoloration is coming from. However, how is this controlled? How can I obtain parts that have the nice black finish? I thought maybe it was the QPQ process, but I have parts with Lindure as well and they are even worse! After a wash is done to remove the oil that the parts were soaked in, you can rub off some of the red discoloration. What can I do to ensure that this doesn't happen? Is this bad that it is?

Thank you!

Christa Austin
Design Engineer - Buffalo, New York
July 15, 2010

Q. I have similar issues with parts finished using Melonite. Unfortunately, it seems no one was able to answer the questions. My part is 1010 steel with 416SS pins fitted into it. It is the 416 pins that are showing the "rust" deposit. What is the cause of this deposit, and is this a normal byproduct of the Melonite process? Thank you.

Alex Mackenzie
tools - Ottawa, Ontario, Canada
January 17, 2014

A. There are 2 types of blackout methods, the first at 140 degrees, the second at 440 degrees. 440 degrees is a healthier process. The other reason for the redness may be that the layer is removed in sandblasting. If your nitration is solid, the blackening will be smooth after polishing.

metamuh tr
- Türkiye
May 31, 2024

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