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I've recently purchased a Damascus knife and am patiently awaiting it's arrival in the mail. I have been researching the potential care and maintenance habits for this craftsman blade, hoping to keep it in pristine condition.

I'm wondering what measure(s) could be taken to prevent a Damascus knife from rusting. I will be crafting the handle from my own scales and pins upon receiving the item, so any manipulation done to the steel can be preformed upon the blade in its entirety. The alloys used are a mix of 1095 and 15n20 steels respectively.

One of the potential means that I've entertained the thought of is bluing, AKA a black oxide finish. Bluing is a method commonly used on gun metal in which various gun parts are submerged in caustic hot salt baths for a period of time in-order to attain the coat. This isn't the only method to obtain the oxide layer, it's but one of many. Some sources have stated that bluing provides rust resistance while others are skeptical since most oxide layers as a result of the process are merely 2.5 micrometres (0.0001 inches) in thickness.

The method I'm most interested in potentially trying is cold bluing. Cold bluing can be achieved either by coating the high-carbon steel in mustard, painting it in a commercially sold "perma-blue formula", or submerging it in an acidic at-home substance such as vinegar or lemon juice (boiling vinegar to enhance the effect).

Here is my question Ultimately TL:DR Can a true rust resistant layer be obtained via cold-bluing methods on high-carbon Damascus steel (1095 & 15n20)? Will the acidic substance such as vinegar or "perma-blue formula" simply eat through the steel with time (while I'm letting the bluing process take place before I've neutralized the blade with something such as baking soda), or will it develop a thicker layer of patina oxide layer? Some sources say the bluing layer is rust, therefore rust can't develop on top of rust. Others say bluing is purely cosmetic and can not prevent rust.

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    $\begingroup$ I don't think you need to change anything in the blade, just be careful that it won't have occasion to rust. Also Damascus steel has distinct pattern which would be lost if you'd oxidated it. $\endgroup$
    – Mithoron
    Jul 6, 2017 at 18:44
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    $\begingroup$ Store it reasonably dry (=not under the kitchen sink) and wipe the blade with an oily cloth from time to time, clean it after use and not on the next day, and use only water to clean it (or oil it directly afterwards if you used soap), and it should never rust. $\endgroup$
    – Karl
    Jul 6, 2017 at 19:29
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    $\begingroup$ i would recommend ezox firearm lubricant, it will leave a dry film of Teflon on the blade till you use it, after use you have to reapply it but that is as easy as wiping oil on it and letting it sit for a few minutes. (its also very good for cleaning off hard to get off things ie tape adhesive/sap/animal blood) $\endgroup$
    – Gun Guy
    Aug 6, 2018 at 18:45

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It provides limited corrosion protection. I would suggest just putting oil on it; more corrosion protection and it will not obscure the surface pattern which is most all that separates Damascus steel from ordinary steels. As I remember regular "bluing" is a complex of ferocyanides ; Oxides of iron are red and black , brown rusts are hydrated oxides. I have now looked at Wiki and see some of the problem. Molten cyanide salts are use to carbonitride steels;I believe these leave a blue surface- you can't do that. Another source of blue ( and straw and purple) color is different thicknesses of very thin oxide layers. I have a chart showing one hour at 540 F (in air) , or 10 minutes at 590 F, or 20 hours at 485 F will produce a blue. Higher temperature and longer time give thicker oxide. The color of the oxide is determined by the thickness. Assuming the blade is hard like Rockwell C 60, these temperatures will cause some softening. The other methods sound like they will etch the steel . Same conclusion, oil it.

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I wouldn’t personally blue a Damascus knife, however I have used commercial blue on high carbon knives and it has added some rust protection a substantial amount more protection I should say than an untreated HC blade.

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