Carbon steels, patina, and rust prevention...

[R.C.Reichert]

I am interested to know if there are any particular types of blade finishes for simple high-carbon steels that help prevent rust formation. Will a steel that is blued or etched with acid be less prone to rusting, or does it make things worse? I kinda like the vinegar etch or the type that Raymond Richard uses on his knives with the ferric chloride. Is having a patina a good thing on a blade? Would for example a damascus blade that has been etched rust as readily as one that was just satin finished? I would appreciate your opinions. Thanks.

 

[kgd]

The patina itself is an oxide layer on top of the steel. As it prevents access to the metal underneath it to oxygen, then yes it does prevent further rust. I force a patina on my carbon knives before going out in the field as it is easier than try to keep the blade constantly wiped clean.

 

[A C Richards]

There are 2 thought on etched finishes. One say yes do it because it holds the oils in place the other say do not because it holds the moisture. Patinas only help so long as the knife is not abused by putting it away wet and dirty. If you allow a knife to patina but take the time to wipe it off and put a light coat of oil when you get back home it will last a lifetime or more. I like my blades to patina. I have been abusing one around the house to see how it will hold up. It has been very surprising to see the lack of corrosion on this blade. It still has pitch on it from the last branches I cut up. A couple of small rust spots but not nearly what i expected.

 

[James_Terrio]

Corrosion-resistance for a using knife is over-rated, in my opinion. I have yet to come across a knife so badly corroded it couldn't be sharpened up and used like new.

Fine finishes deter rust by reducing the surface areas where it can begin. Patinas deter by putting a thin layer of oxide on the steel. Either will require some minor maintenance to keep it nice and perfect, the patina requires less care.

Some will say the best patina comes from years and years of use. You end up with a blade that may be dark, mottled or even browned in appearance, but has suffered no loss in performance.

Mr. Richards, I don't understand about etches "keeping oils in" or "keeping moisture in". I clean my blades very well with soap and water, dry them, then a quick acetone wipe before doing any patina. I thought this removes all the moisture or oils on the steel?

 

[Will Leavitt]

James,
Not to put words in his mouth but I'm guessing it's the "surface area" argument. An etched or hand rubbed blade has more surface area to accumulate moisture or to hold onto oils. A mirror buffed blade has less surface area to either hold moisture or oils.

 

[James_Terrio]

Ok, I understand that. Thanks!