Help Identifying Green Substance

[BrothersKeeper]

Seeking some help here ... I have several knives that have a green substance on nickel silver bolsters, pins and shields. This is not the soft green verdigris typically scene when nickel silver is in contact with leather for years. Instead, these are hard green deposits that seem to appear when the knives are in contact with some types of foam or other material in display boxes. It is not easily polished off. I have attached a photo of this and wonder if any of you have seen it, know what it is and know how to remove it. Thanks in advance for all info.

[Sharpnshinyknives]

Is this on both sides or just the side against the foam? I’ve had good luck using mineral oil on a green substance I’ve seen on stag. You might try that or simply use Simichrome or Case Paste to polish it off.

[BrothersKeeper]

Thanks Sharpnshinyknives ... typically it is on one side only. But sometimes there is a less obvious contamination on the other side. I suspect it is some kind of chemical reaction between the silver and the chemistry in the foam. I can give it a shot, but this stuff is tough.

[rea1eye]

I am thinking the foam is reacting with the silver on the knife. If I remember
correctly, there are some types of foam which are non-reactive.

Bob

"Industrially, formaldehyde is produced by catalytic oxidation of methanol. The most commonly used catalysts are silver metal or a mixture of an iron oxide with molybdenum and/or vanadium. " Source: Wikipedia 9.27/23

[tvic]

Never seen this before, but I always use Wenol on bolsters and blades. Can’t guarantee any results here, but it sure helps with dull bolsters - and even minor surface scratches.

[ea42]

It's a type of verdigris caused by VOC offgassing of the foam. This is especially common in the older foam packaging from the 70's and 80's. Much like the verdigris you get when you store a knife in a sheath for long periods.

Eric

[BrothersKeeper]

Many thanks to Bob, Tom and Eric for your thoughts. Eric you sound like you have run into this before. Do you know how to get rid of it? Like I said it is very hard deposits; is there anything that will soften, dissolve it? Chet

[btrwtr]

Good information above. You might try using an oil or simichrome polish as mentioned in combination with 0000 steel wool. Let us know how you make out.

[deo-pa]

Nickel silver is roughly 60% copper, and 20% each of nickel and zinc. Based on the color, your corrosion certainly looks like the surface copper oxide normally produced when copper or copper alloys come in contact with air / water, however that oxide is not so tenacious as yours seems to be. The typical remedy for that is lemon juice with baking soda or lemon juice with salt (dissolve the salt so it doesn’t scratch).

You might try one of those, which won’t hurt the knife as long as you thoroughly rinse and dry it. However, even if those remove the green corrosion they may leave behind pitting because in your photo it looks to me like the corrosion is not just on the surface.

You are probably right that the corrosion is the result of a reaction with a chemical released by the foam, either a volatile organic as suggested above or an element within the foam. It is probably not sulfur, as that produces a black-colored corrosion on copper.

Dennis

[rea1eye]

I agree with what was said. What I would do is apply vinegar or lemon juice over area by soaking a paper towel and
drape over the affected area for an hour.
rinse with water, dry completely
then buff with 0000 steel wool
then buff with semichrome or other polishing cream.

Let us know how it turned out.

Bob

[ea42]

Simichrome should work on that, you may just need multiple applications and a good amount of elbow grease. I use a small folded up piece of paper towel for the application and scrub, then a soft cloth to polish off the residue. If that doesn't work you can go with stronger methods. If your blades are carbon steel any acids will stain them so if you need to go with a vinegar or lemon juice soak I'd do what Bob suggested and soak a small strip of paper towel, just wide enough to drape over the bolster only, and let it sit for a while, then polish.

Eric

[1967redrider]

When I enlarge the picture, it looks like pitting to me.

[BrothersKeeper]

Thanks to everyone for their answers. I will give it a try and let you know what happens. Chet

[RedRaiderRick]

I get the same stuff on ammo stored in leather loops on a gunbelt. Tumbled for hours in pecan shell media with no effect. Think I tried fingernail polish remover and alcohol to softern and then scrub off. That might damage the scales though so be careful.