Cleaning rust on vintage stainless steel knives

[avigo]

I have a few US military folding utility knives (the all stainless ones) that have some small rust spots. Some wipe away easily with mineral oil but some are stubborn, mainly inside by the springs.

What are some safe ways to clean this? I've heard to not use vinegar but that a baking soda paste might work.

Any other suggestions? I really want to avoid steel wool or anything abrasive. Thanks

 

[Obsessed with Edges]

For just small spots on stainless, the baking soda paste should work well enough to scrub away any loosely attached red rust. On stainless steel, I wouldn't worry too much about whatever remains beyond that, as red rust won't likely take a strong hold in the steel anyway.

I've liked using the wooden sticks from popsicles or ice cream bars for a scrubbing tool inside the bladewell of folding knives. Can also buy the sticks in bulk in the crafts section of stores like Walmart or Hobby Lobby as well (usually labeled as 'craft sticks'). You can whittle a point on the stick to reach into tight corners of the pivots with that. Could be used in conjunction with the baking soda to scrub the inside face of the springs. Baking soda will completely dissolve as well, when some water is added. So there's little risk of any baking soda grit remaining in the pivots after using it. Just rinse it all thoroughly. And baking soda isn't hard enough to be abrasive on the steel itself, but only on the relatively soft rust on the surface.

I have a Victorinox SAK that was left in a tool box in the covered bed of a pickup for several years, in a wet/humid climate. It rusted enough to make opening the blades difficult. It was more extreme than just a few spots of rust. For that one, I soaked it in WD-40, then wrapped it in paper towels also saturated with WD-40, and sealed it all in a zip-loc bag for a few days' time (4 days or longer, IIRC). That helped to soften and loosen up the rust in the pivots, which then made it somewhat easier to open the blades (with the aid of pliers). After that soak, I continued to saturate it with WD-40 while opening & closing the blades to work the rust out further. So long as the WD-40 was flowing red/brown while doing that, I kept spraying it. After it started running clearer, I then gave the whole thing a bath in warm water with liquid dish detergent and flushed out all the WD-40, rinsing in hot water (evaporates more completely to make drying easier), then oiled the joints. I don't think you'd need to take such extreme action for your knives, based on your description of the rust. But I include this just as another option if you feel it can help.

 

[Grasshopperglock]

Passivate it. There's many a passivation solution on the market. Citric acid is popular and you can get it from the grocery store.

 

[avigo]

Passivate it. There's many a passivation solution on the market. Citric acid is popular and you can get it from the grocery store.

That might be a little more involved than I need for this particular project but I'll definitely look into it!
How harsh is this process? Really looking for something that will be easy on the knife since it is only a few small spots that need attention.

 

[avigo]

For just small spots on stainless, the baking soda paste should work well enough to scrub away any loosely attached red rust. On stainless steel, I wouldn't worry too much about whatever remains beyond that, as red rust won't likely take a strong hold in the steel anyway.

I've liked using the wooden sticks from popsicles or ice cream bars for a scrubbing tool inside the bladewell of folding knives. Can also buy the sticks in bulk in the crafts section of stores like Walmart or Hobby Lobby as well (usually labeled as 'craft sticks'). You can whittle a point on the stick to reach into tight corners of the pivots with that. Could be used in conjunction with the baking soda to scrub the inside face of the springs. Baking soda will completely dissolve as well, when some water is added. So there's little risk of any baking soda grit remaining in the pivots after using it. Just rinse it all thoroughly. And baking soda isn't hard enough to be abrasive on the steel itself, but only on the relatively soft rust on the surface.

I have a Victorinox SAK that was left in a tool box in the covered bed of a pickup for several years, in a wet/humid climate. It rusted enough to make opening the blades difficult. It was more extreme than just few spots of rust. For that one, I soaked it in WD-40, then wrapped it in paper towels also saturated with WD-40, and sealed it all in a zip-loc bag for a few days' time (4 days or longer, IIRC). That helped to soften and loosen up the rust in the pivots, which then made it somewhat easier to open the blades (with the aid of pliers). After that soak, I continued to saturate it with WD-40 while opening & closing the blades to work the rust out further. So long as the WD-40 was flowing red/brown while doing that, I kept spraying it. After it started running clearer, I then gave the whole thing a bath in warm water with liquid dish detergent and flushed out all the WD-40, rinsing in hot water (evaporates more completely to make drying easier), then oiled the joints. I don't think you'd need to take such extreme action for your knives, based on your description of the rust. But I include this just as another option if you feel it can help.

Thanks! Very helpful.

Does using a hairdryer or something help with quickly drying wet knives after cleaning or is that not needed? Just want to avoid creating more rust as I go

 

[Grasshopperglock]

That might be a little more involved than I need for this particular project but I'll definitely look into it!
How harsh is this process? Really looking for something that will be easy on the knife since it is only a few small spots that need attention.

It's boiling the steel in water with citric acid. It'll remove the iron on the stainless steel surface. Not only does it remove what caused the rust. It prevents the stainless from rusting.

The process is used after welding stainless. Where the iron will come out the stainless and will lay on top the surface.

Any welding shop worth their beans will carry a Passivate spray. Spray on, wipe off. Boiling in citric acid is the DIY method.

 

[Don_Logan]

Kroil

 

[Obsessed with Edges]

Thanks! Very helpful.

Does using a hairdryer or something help with quickly drying wet knives after cleaning or is that not needed? Just want to avoid creating more rust as I go

With stainless steel, if it's rinsed in hot water, it shouldn't matter too much. Hot water rinsing warms up the steel and will do a lot to evaporate off any moisture left. Any residual moisture should evaporate soon enough anyway, to avoid any risk of further rusting.

You could also drizzle some isopropyl alcohol through the internals of the knife to carry away any residual moisture.

And you can use the hair dryer if you want to. You'd likely not need that, in this case. But it certainly won't hurt anything, if you want to.

With stainless steel knives, you shouldn't have to do anything more extreme. Most rusting in stainless is a result of exposure to corrosives like saltwater or acids/caustics, or just inattention to keeping the knife clean & dry over a very LONG period of time. If the knife will be handled & inspected on a regular basis, it'll be easy to keep it clean & dry enough not to worry anymore about it. Just wiping it down with some Windex on a clean rag or paper towel is enough on a day-to-day basis. That's how I 'clean' my stainless knives most of the time, after use or handling.

 

[Bill DeShivs]

Why wouldn't you want to use steel wool?
0000 steel wool, used gently, should remove surface rust without harming the metal. I use it every day in my restoration work.

 

[Grasshopperglock]

Steel wool is the worse. It leaves iron on the stainless and will make it rust even more.

That's why we don't use a steel brush on stainless. You can use a stainless brush or brass but never steel.

 

[Cementite]

In my experience working on saltwater boats, the big problem with stainless steel is crevice corrosion. If you get scratches in the SS (like from a wire brush, and that goes for ANY wire brush whether it's carbon steel or stainless), what happens is, moisture gets into the crevice or scratch, and on a microscopic level what you get is a galvanic cell (this is how batteries work), with iron on one side and nickel (or chromium or any other dissimilar metal in the alloy) on the other (again, this is on a microscopic level). If there's any electrolyte in the water/dew that's in the scratch or crevice (dissolved CO2 is all it takes, although saltwater works better), you will get electrical current moving between the dissimilar metals, along with galvanic corrosion. This can "activate" the stainless steel, and after that, it's off to the races with corrosion/rust...

Personally, I'd probably use something like Kroil (or ATF mixed with acetone), and use wooden toothpicks, ice pop sticks, etc., to try to work the rust out. Then I might use some steel wool with Kroil and try to scrub out any of the rust scale as well as possible. Then I'd wash it real well with hot water and Dawn, then dry it, then keep a good coat of oil on it. Kroil (or ATF and acetone) really soak into all the crevices and help prevent further corrosion...I think the key is removing as much of the "tooth" as possible since that is where moisture will tend to condense and collect. Then keep the pits filled with oil or wax or whatever...there's also a material called Fluid Film that works real well to protect metals (they use it on bare steel inside saltwater ships and it lasts a long time). It contains lanolin (also an ingredient in the famous "Ed's Red" gun cleaner) and lanolin really seems to stick around and protect metal from rust in my experience.

 

[Bill DeShivs]

Steel wool is the worse. It leaves iron on the stainless and will make it rust even more.

That's why we don't use a steel brush on stainless. You can use a stainless brush or brass but never steel.

Well, I'm glad you shared that with us.
But, it doesn't work that way. All you have to do is clean the steel wool residue off. Even if you don't it seldom makes any difference-at least over the last 50 years in my knife restoration shop....

 

[killgar]

In my younger days I worked in a few restaurants as a dishwasher. I scrubbed more stainless steel pots and pans with steel wool than I care to remember. None of them rusted.

And in my own life I've used SOS pads to do the same thing. Again, no rusty pots and pans.

 

[Obsessed with Edges]

Might be worth posting a pic or two of the small rust spots as described on the knives mentioned. I'm getting the sense here, in reading some of the replies, that some suggested methods and debating pros/cons of each may be WAY MORE complicated than is needed and might just confuse things more than is warranted. Keeping stainless steel relatively free of rust is almost always a very easy thing to do, with the simplest methods usually being the best. Stainless steel will do most of the work to protect itself, most of the time, unless it's exposed to something very corrosive and/or just neglected for way too long.

(Having said the above...)

One other thing I've done, which is kind of cool in how it works, is to just dab a little paste mix of Bar Keepers Friend powder & water on isolated spots of rust on stainless steel. Let it sit for no longer than 60 seconds or so, and then thoroughly rinse it off under running water. Bar Keepers Friend has a little bit of oxalic acid in the mix, which dissolves rust. It's a pretty light concentration, but still strong enough to etch stainless steel if it's left in contact too long. On stainless steel, somewhere between 30 - 60 seconds of time in contact is enough to get the job done. Use a cotton swab or something similar to dab it onto the spots. Wait 30 seconds or a minute, then rinse it away. This method may in itself be more than is really needed, most of the time. I've done it just a very few times. But it's also very easy, in the sense that little or no scrubbing is needed to make it work.

 

[avigo]

Why wouldn't you want to use steel wool?
0000 steel wool, used gently, should remove surface rust without harming the metal. I use it every day in my restoration work.

I've never had good luck with steel wool. It always leaves micro scratches but it might if I can't get the rust off with other methods I might try it

 

[avigo]

Might be worth posting a pic or two of the small rust spots as described on the knives mentioned. I'm getting the sense here, in reading some of the replies, that some suggested methods and debating pros/cons of each may be WAY MORE complicated than is needed and might just confuse things more than is warranted. Keeping stainless steel relatively free of rust is almost always a very easy thing to do, with the simplest methods usually being the best. Stainless steel will do most of the work to protect itself, most of the time, unless it's exposed to something very corrosive and/or just neglected for way too long.

(Having said the above...)

One other thing I've done, which is kind of cool in how it works, is to just dab a little paste mix of Bar Keepers Friend powder & water on isolated spots of rust on stainless steel. Let it sit for no longer than 60 seconds or so, and then thoroughly rinse it off under running water. Bar Keepers Friend has a little bit of oxalic acid in the mix, which dissolves rust. It's a pretty light concentration, but still strong enough to etch stainless steel if it's left in contact too long. On stainless steel, somewhere between 30 - 60 seconds of time in contact is enough to get the job done. Use a cotton swab or something similar to dab it onto the spots. Wait 30 seconds or a minute, then rinse it away. This method may in itself be more than is really needed, most of the time. I've done it just a very few times. But it's also very easy, in the sense that little or no scrubbing is needed to make it work.

I agree. I probably should have posted a pic earlier, will try to do that.

I do appreciate all of the info here. Helps if I run into a more complicated/rusted knife project

 

[Another Shepherd]

The CRK web site recommended Soft Scrub All Purpose for cleaning blades, last time I looked. It works fine for removing light rust and stubborn food residue. And I like the non-scratch scouring pads from Dollar Tree, 6 for $1.25. This is all very convenient, since I also use it for pots and pans and dishes.

 

[Tensaw]

Kroil

This.

 

[Grasshopperglock]

Man...over 300 views.


So has anyone passivated their stainless steel? Pickled it?

The citric acid from the store. Like 2 tablespoons or a good long pour in a pot of water.

I'm surprised the welders haven't mentioned this to the knife guys before.

Not only can you remove it. You can prevent it with zero harm to the stainless.

 

[Blade Lab]

The guy from Alexandria Knife Sharpening recommends CRC Evapo-Rust, which is a water-based, non-acidic rust converter. I picked some up, but haven't had occasion to try it out yet.