hydrogen embrittlement

[ISKski]

I had asked about slow rust bluing in a previous post but it garnered little response (thanks Stacy for being the sole respondent) anyway I decided to skip it for the last project and try it on the current project (15n20).

Basic Process is mix hydrogen peroxide, vinegar, and salt - apply solution to let piece rust - card off excess rust - boil …. Repeat till desired color achieved

Further research led me to the concept of hydrogen embrittlement - my understanding is: exposing hardened steel to hydrogen at a temp lower than 150°c can impart hydrogen atoms on the surface of the steel causing the piece to crack.

is this slow rust bluing a viable process for darkening a blade , or am I guaranteed to crack the knife I’ve been working on for the last several weeks ?

 

[Bill DeShivs]

I have never known rust bluing to cause hydrogen embrittlement.
Plating is known to cause it.
Regardless-there is a low temperature tempering process that eliminates the embrittlement. Seems like around 300 degrees or so. I'm sure a search will find it.

 

[A.McPherson]

I'm going to go out on a limb and say "No".
Rust bluing has been used for a LONG time to blacken steel, especially in the firearms industry. Barrels, receivers, bolts, all of em used to be rust blued. If it made them brittle, it wouldn't have been used.

 

[Stacy E. Apelt - Bladesmith]

Short answer - It is not an issue to worry about.
Second answer is - If you worry about it do a one-hour 300°F temper and any embrittlement is gone.