Aluminum foil

[lowell holmes]

For some new woodworkers that may not know, if you wrap a flat file with aluminum foil, the file will not rust.
Galveston County Texas is rough on files.

[Pat Barry]

Why is that? Aluminum foil keeps out moisture? Chemical reaction?

[Phil Mueller]

Aluminum foil sprayed with WD40 is also a very good way to scrub away rust.

[Mike Henderson]

Why is that? Aluminum foil keeps out moisture? Chemical reaction?

I'm just guessing but a properly wrapped aluminum foil could be air tight and keep out moisture.

Mike

[Anuj Prateek]

It possibly serves as a sacrificial layer. It will get oxidised before steel.

[Pat Barry]

Aluminum foil not going to be much of a sacrificial material compared to steel. Aluminum oxixizes rapidly but doesn't build any significant thickness. It is a very effective moisture barrier though as mentioned by others.

[lowell holmes]

Just try it. You will be amazed.

[Jacob Reverb]

I suspect it has something to do with aluminum's excellent thermal conductivity (only three metals – gold, copper and silver – are more thermally conductive) moving heat into the files without getting them wet from condensation/dew and thus rusting them...

On the other hand, you could probably do the same thing with plastic Saran wrap, which ain't very thermally conductive. Or light oil/kerosene.

[Malcolm McLeod]

I suspect it has something to do with aluminum's excellent thermal conductivity (only three metals – gold, copper and silver – are more thermally conductive) moving heat into the files without getting them wet from condensation/dew and thus rusting them...

On the other hand, you could probably do the same thing with plastic Saran wrap, which ain't very thermally conductive. Or light oil/kerosene.

Lowell is right. It’s called cathodic protection - based on electrical conductivity, not thermal.

The dissimilar metals form a battery, where in this case the aluminum is the sacrificial anode.

It’s common method to protect ships hulls, pipelines, storage tanks, etc... And generally it’s not necessary to 100% wrap the steel in the aluminum to protect it; the two just need to have good electrical contact. (But wrapping it can’t hurt!:))

[Ben Rivel]

Hmmm.... Can I wrap my entire table saw top in foil when not in use then? ha ha

[Stan Calow]

This explains why my head doesn't rust.

[Ben Rivel]

This explains why my head doesn't rust.
LOL. Also good for blocking the mind control from aliens or 5G!

[Jacob Reverb]

Lowell is right. It’s called cathodic protection - based on electrical conductivity, not thermal.

The dissimilar metals form a battery, where in this case the aluminum is the sacrificial anode.

It’s common method to protect ships hulls, pipelines, storage tanks, etc... And generally it’s not necessary to 100% wrap the steel in the aluminum to protect it; the two just need to have good electrical contact. (But wrapping it can’t hurt!:))

Well, and you also need to submerge the dissimilars in an electrolyte. I'm not sure a bit of condensation on the surface of the aluminum foil is gonna work, particularly if you completely wrap the steel file. (Also, it's not differences in electrical conductivity, but rather differences in electrode potential.)

Yeah, I run boats in the ocean and am familiar with galvanic corrosion. It eats stuff up. A pencil line across a stainless prop shaft is a good way to lose a wheel.

[Zac wingert]

Don’t know a lot about this, but seems like some sort of electrolysis (sp.?)

[Malcolm McLeod]

Well, and you also need to submerge the dissimilars in an electrolyte. I'm not sure a bit of condensation on the surface of the aluminum foil is gonna work, particularly if you completely wrap the steel file. (Also, it's not differences in electrical conductivity, but rather differences in electrode potential.)

Yeah, I run boats in the ocean and am familiar with galvanic corrosion. It eats stuff up. A pencil line across a stainless prop shaft is a good way to lose a wheel.

I may be getting way out in the weeds and I am certainly stretching the brain cells pretty thin here, but there are differing quality electrolytes. Saltwater obviously is decent, but I dimly recall air can serve as an electrolyte too, just a really, really poor one....???

[Jacob Reverb]

I dimly recall air can serve as an electrolyte too, just a really, really poor one....???

In the absence of plasma, I think air performs far better as an insulator than as an electrolyte. ;)

In other words, to get galvanic corrosion between dissimilar metals "submerged" in air, I suspect it's gonna take something on the order of 13.8 billion years. YMMV

[Malcolm McLeod]

In the absence of plasma, I think air performs far better as an insulator than as an electrolyte. ;)

In other words, to get galvanic corrosion between dissimilar metals "submerged" in air, I suspect it's gonna take something on the order of 13.8 billion years. YMMV

I guess I'll have to go dig up my Chemistry professor and scold him.:mad: I'd also guess that with the foil touching the file, an electrolyte becomes somewhat less important.;)

...like I said, waayy out in the weeds.

[Jacob Reverb]

I'd also guess that with the foil touching the file, an electrolyte becomes somewhat less important.;)


Not true. Without an electrolyte, there will be, and can be, no galvanic corrosion. Not sure how to say it any plainer.

Dissimilar metals in air don't galvanically corrode. Otherwise, everything that was ever plated would corrode to pieces. (This happens, but only with an electrolyte.)