Electrolysis: Dark blue oxide from steel?

[Alex Linton]

TL;DR Summary

Dark blue oxide formed from putting alloyed steel through electrolysis, is this copper oxide?

Hi there,

I have been trying to make iron oxide through electrolysis, I am using salt water as the electrolyte and an old alloyed steel (I am assuming iron and carbon) square pipe as the anode and a Rebar cathode.
Unfortunately the beaker gets filled with this dark bluey color and when letting it settle before decantation I can see a thick dark blue layer of sediment underneath a much finer orangey brown layer, the latter of which was the only one I was expecting.

I Wanted to ask what that layer could be or how to identify it? it looks like maybe copper oxide? but i thought that was more of a light blue. Also there is "blue iron oxide" but that is obtained in what i thought was a different process. It definitely sinks to the bottom of the solution allot faster than the iron does if that helps.

If it is copper oxide, a friend of mine would like to use it in glacé for pottery.

Thanks so much for your time :)

 

[Alex Linton]

I am so sorry i think i was being dumb. Its probably iron hydroxide right?

 

[Bystander]

https://www.cratex.com/gunsmith-tools-supplies/gun-bluing

 

[Borek]

I am so sorry i think i was being dumb. Its probably iron hydroxide right?

Not necesarilly. These hydroxides are unstable and decompose rather quickly, producing mixture of hydrated hydroxy oxides. The red layer is definitely that, just dominated by Fe(III). Black in the context of iron oxides suggests FeO or a mixed oxide Fe₃O₄.

TBH I have no idea what it is. Some mixture of hydrated oxides is quite possible, but the color throws me off. I can be wrong, but far as I understand this bluish tint is not a property of the compound itself, it is rather result of the exact crystalline form and is more common in the oxide produced at high temperatures on the metal surface. I am not sure it can be visible in a wet sludge.

Are you sure it is not actually greenish? These tints are often quite difficult to describe, but there is something called a green rust, which is kind of a mixed hydroxy salt.

 

[RowieK]

Isn't it possible that the iron you tried to electrolyse contained traces of copper?
The blue-ish color of the solution is making the question hard to solve.
But like Borek said, are you sure it isn't greenish? Then it would make a little more sence.

 

[chemisttree]

You could try a flame test? Should be green flame if copper. Smear a little on some paper and when dry, ignite. Look for traces of green flame.

 

[daschergunsmithing]

TL;DR Summary: Dark blue oxide formed from putting alloyed steel through electrolysis, is this copper oxide?

Hi there,

I have been trying to make iron oxide through electrolysis, I am using salt water as the electrolyte and an old alloyed steel (I am assuming iron and carbon) square pipe as the anode and a Rebar cathode.
Unfortunately the beaker gets filled with this dark bluey color and when letting it settle before decantation I can see a thick dark blue layer of sediment underneath a much finer orangey brown layer, the latter of which was the only one I was expecting.

I Wanted to ask what that layer could be or how to identify it? it looks like maybe copper oxide? but i thought that was more of a light blue. Also there is "blue iron oxide" but that is obtained in what i thought was a different process. It definitely sinks to the bottom of the solution allot faster than the iron does if that helps.

If it is copper oxide, a friend of mine would like to use it in glacé for pottery.

Thanks so much for your time :)

I don't know if your still watching this but I had the same thing happen when I mixed up prices of cobalt steel for magnetic shielding in my nickel pile. So the super blue may be cobalt.