Removing Rust from an black oxide coated blade

[Freedman]

Hello fellow Knive people!
I hope you can understand my wording well, as English is not my first language.
I hope you can help me with the following problem:

A few years ago i gifted an friend an "Kubey Flash KU158" folding knife, which is partially covered with black oxide as an finish. Now he neglected the knife for some time and showed me pictures of some rust and asked me, if i can remove it for him:

My go would be, to throw the blade in my ultrasonic cleaner with some cleaning solution, but i am afraid that the finish will go off as well.
How would you handle this? Any experiences on de-rusting black-oxide finishes?

Thank you very much in Advance and friendly Greetings,

Lukas from Germany

 

[Robert Ptacek]

Welcome aboard! I would try using Flitz to remove the rust spots. It is a very good polishing compound.As a disclaimer I have never used it on a black oxide finish.You could use it on the whole blade to blend the finish.Good luck.

 

[Obsessed with Edges]

Be careful with Flitz or other polishes. It will likely remove or alter the black oxide or any patina. I'm assuming the factory black oxide is just simply iron oxide, which comes off pretty easily with any polishing. I learned this the hard way, with one of my blades (damascus, with a dark oxide etch).

If the spotting and the factory oxide are both iron oxide, it'd be difficult to remove one without altering the other. So long as there isn't any RED rust in the spotting, I'd be inclined to let it be. For any red rust, rubbing with some baking soda or very fine steel wool (#0000) and some oil or WD-40, is one way to clean that up without damaging the black oxide or any other patina. The dark oxide spotting would still remain, although it's completely non-destructive and harmless to the steel.

 

[Freedman]

Thank you very much for the answers and the welcoming!

If the spotting and the factory oxide are both iron oxide, it'd be difficult to remove one without altering the other. So long as there isn't any RED rust in the spotting, I'd be inclined to let it be. For any red rust, rubbing with some baking soda or very fine steel wool (#0000) and some oil or WD-40, is one way to clean that up without damaging the black oxide or any other patina. The dark oxide spotting would still remain, although it's completely non-destructive and harmless to the steel.

So as far as i understood, i dont have many coices to remove just the spotting, without also changing the black layer.
He will send it to me soon and i will inspect it further on how deep the spots go and if some spots are red.
How would one go about trying to remove the spots with Baking-Soda/Steel Wool? Use it on the whole blade/area or apply it to an Q-Tip and work very punctual?
My Goal would be to leave the whole finish as uniform as possible.
He will send it to me anyways for sharpening, cleaning and oiling, so i will see if i can remove them without damaging the finish.
Also, putting it in an Ultra-Sonic Cleaner with some deruster would be just as bad for my goals, because both the coating and the rust are iron oxide, which will fade after treatment, right?

Greetings, Lukas

 

[killgar]

If it were my knife, I would sand the blade and give it a satin finish. It appears to be D2 steel, my experience with D2 is that although it will rust, it is not heavily prone to rusting. D2 is a "near-stainless" steel.

I don't see any way of saving that finish. And it doesn't appear that the finish has much value anyways. I'm guessing its just for the look. If the finish isn't going to protect the blade from rusting, and if the blade is going to continue to be exposed to moisture, I'd rather have a satin finish so I could more easily remove any future rust.

 

[Obsessed with Edges]

Thank you very much for the answers and the welcoming!



So as far as i understood, i dont have many coices to remove just the spotting, without also changing the black layer.
He will send it to me soon and i will inspect it further on how deep the spots go and if some spots are red.
How would one go about trying to remove the spots with Baking-Soda/Steel Wool? Use it on the whole blade/area or apply it to an Q-Tip and work very punctual?
My Goal would be to leave the whole finish as uniform as possible.
He will send it to me anyways for sharpening, cleaning and oiling, so i will see if i can remove them without damaging the finish.
Also, putting it in an Ultra-Sonic Cleaner with some deruster would be just as bad for my goals, because both the coating and the rust are iron oxide, which will fade after treatment, right?

Greetings, Lukas

With baking soda or steel wool, just scrubbing the rust spots is enough. In that use, both are working just as a mild abrasive - it's hard enough to scrub away red rust, which is pretty soft and weakly-bonded stuff - but not hard enough to scratch the steel or the black oxide layer, which is stronger and more durable than the red rust.

I'd avoid ANY kind of chemical treatment, such as the deruster used in the ultrasonic cleaner.