Rust on knives

[psarou]

Just wondering about the subject. How much rust does it take to ruin a knife beyond repair? Can you bring a knife back from rust issues and what's the best way?
Thanks kindly

 

[Makoto Pat]

This is perhaps best left in the hands of more learned men than I, BUT...I have recently restored some old draw knives and spoke shaves and carbon steel blades with an old bit of chemistry. Take said steel (if possible remove any brass furniture, pins are okay. Note: I am not certain what other metals will be ruined by this...like shiny engraved items) place in a large zip lock baggie with lemon juice and a dash of salt. Wait a few hours. Removed from baggie and use a dish scrubbing pad (non-abrasive) and some WD-40 or 3-in-1 oil. I prefer the oil. Repeat in necessary. After finished I like to give the steel a little alcohol massage. Then re-oil lightly.

I hope this helps. If pits are present...This will not remove them.

 

[Planterz]

Do you have a rusty knife, or are you planning on letting one rust? What kind of steel are we talking about? What kind of knife?

 

[bpeezer]

Hydrofluoric acid does the trick pretty well. I would only consider a knife "beyond repair" if the tang rusted out (fixed blade) or the pivot area rusted out (folder). The majority of the blade should be in good condition after removing rust, then you can grind and reprofile the blade to work well again. It won't be the same knife, but it would still be a knife!

 

[goodeyesniper]

it takes a lot. I'd wager you could leave the average carbon steel blade out in the elements unprotected for an extended period of time and get it back to working shape with a little elbow grease and a small amount of time and abrasives.

rust is a widely over blown issue for all but sea faring folk, or neat freaks who need a spotless blade, IMO.

if you are in a particular humid, wet, or otherwise corrosive environment, about the worst that will happen in the short term is some mild edge degradation and some spots in the finish.

it takes extreme neglect for the elements to actually do lasting damage to a blade. I guess if it's a folder it could get a bit of a gritty action that might not go away, but that is once again if it's a pretty bad case.

 

[David Martin]

Good point ^. DM

 

[Obsessed with Edges]

This is one of those 'you'll know it when you see it' things, as I view it anyway. Usually, if some time is spent inspecting and cleaning an old, rusty knife, it'll become obvious at some point whether the knife has any useful life left in it. With a folding knife, if it's so rusted that the blades are fused shut, to the liners or the backspring, that's usually (for me) time to declare 'time of death' for it. Difficult to avoid breaking backsprings, when they're that bad. But if the pivots & springs are still functional (maybe with some aggressive cleaning), I won't write it off so quick. Sometimes the blades themselves will endure a lot more, for a lot longer, and can be scrubbed clean and given new life. Some of that old, time-hardened steel can amaze you in the edges it'll take. An old, ugly, dirty, rusty knife can end up being a favorite user, with some investment in time and elbow grease.

For really neglected knives, the first thing I've always done is to soak/drench/flood the whole thing with WD-40, then wrapped paper towels around it, also WD-40 saturated, and put the bundle in a zip-loc for a few days (3-4 or longer). This has worked to help loosen folders that don't want to open easily, and it'll loosen up a lot of the surface rust, which can be wiped or scrubbed off with paper towels or steel wool. After taking it out, I'll flush it again in WD-40, and keep doing so until it runs fairly clean. Then start exercising the joints by opening/closing the blades, again keeping them wet with WD-40 while doing so.

Assuming that's productive, after all that I'll give the knife a bath in hot water and dish detergent (Dawn/Ivory/etc), and keep working the joints while doing that (while immersed in the soapy water). Rinse in hot water and dry everthing out, then lube the joints.

THEN, that's when I'll start looking at sanding or other means to further clean up the blades (pitting/embedded rust, etc).

David

 

[psarou]

Wow! Thank you everyone for this education. I was one of those, OMG! Rust!!! My knife is ruined! I will never look at a rusty knife the same way again. It can be brought back to life in most except extreme cases.