Forced patina

[germ1]

Forced a patina last night on a 1095 blade, and I always saw people saying that red rust can't form ontop of black rust. Well, they're wrong, I left my knife out(not sitting in the vinegar) last night after already having a dark black patina on it. When I woke up in the morning I found red rust forming all over the knife ontop of the black. I had to sand it all off, now I have to start the patina over again, although I don't see the point since it offers virtually no proctection anyway.

 

[herektir]

You had a FRESH forced patina, likely very thin. Maybe after your forced patina there was very small amounts of vinegar left on the blade which started the rust? Patina helps protect from rust, but wont absolutely stop it. Liken it to fresh steel surface rusting in 4 hours, a patina may make it last a day or 2 in similar circumstances.

I dont oil my blades, I let my patina do its job but i do wipe them off of excess moisture after use. I get no rust on them.

 

[spketch]

It doesn't prevent red rust, just slows it down a bit.

Its important to completely wash off whatever acid you use for forcing a patina. As you experienced, even the residue will continue to react with the steel. Better luck on the next round.

 

[smokinbasser]

Neutralizing the etch chemicals is very necessary after completing the etch to your satisfaction or it will continue if the metal is exposed to oxygen and moisture. Oil or ren wax will stop the process. Using a base chemical will neutralize the acid and its effects.

 

[Obsessed with Edges]

Forced a patina last night on a 1095 blade, and I always saw people saying that red rust can't form ontop of black rust. Well, they're wrong, I left my knife out(not sitting in the vinegar) last night after already having a dark black patina on it. When I woke up in the morning I found red rust forming all over the knife ontop of the black. I had to sand it all off, now I have to start the patina over again, although I don't see the point since it offers virtually no proctection anyway.

What did you clean the blade with, after forcing the patina with vinegar? If you didn't clean it, or if you just rinsed it off with water, the leftover vinegar (acid) is what did the damage.

On the 2nd attempt, scrub the blade thoroughly with baking soda after finishing with the vinegar. Baking soda neutralizes any acidity left (this is the most important part), and will also work to scrub away red rust and some of the loosely-bound black oxide, leaving a more even grey patina behind. Use a little water to mix the baking soda to a paste consistency, and keep scrubbing with it until you no longer see any discoloration (red/brown/black) in the baking soda. Then wash/rinse it all thoroughly, dry everything out and lube as needed.

As mentioned, a patina will slow down rust somewhat. It's value is more noticeable in minimizing the spotting that otherwise takes place on an un-patinated blade. But the blade still needs to be kept reasonably clean & dry when stored for the night. The only thing that comes close to preventing rust completely is stainless steel; and even that's not totally rust-proof.


David