Is graphite lubricant safe for metal parts? [solved]
I've heard an opinion that using graphite lubricant on door hinges can lead to metal abrasion and damaging the hinges. The idea is that graphite has abrasive properties and thus can damage metal.
Is this true? Should I use graphite lubricant on door hinges and similar metal parts around the house?
After reading @woodchips answer and throwing in my $0.02 offhand, I did a bit of research. I found this article on the use (or non-use) of graphite on aircraft. The article mentions that metals such as aluminum, magnesium, zinc, and cadmium may experience galvanic corrosion when exposed to graphite lubricant. Since galvanic corrosion requires an electrolyte, you might be okay if your metal components are inside, and not in a wet area.
The article also mentions that graphite can damage stainless steel at high temperatures. (Probably not going to be an issue in a home though. If it is, you may have other problems like a house fire, and probably won't care much about your hinges at the moment.)
While I am not a chemist, this goes against anything I understand about carbon and its common chemical forms. In the crystalline diamond form, carbon is extremely hard and quite useful as an abrasive. However, in the form of graphite, carbon lies in sheets that are very loosely bonded to each other. These sheets can easily slide against each other under shear stresses because of the very weak bonds, so graphite forms an excellent lubricant.
I would suggest your source is incorrect.
Graphite is very soft and shouldn't cause any excessive metal on metal wear. It is a very effective dry-film lubricant, just a little messy to work with.
I've used graphite to lubricate all the lock cylinders in my cars, house, etc for years. I recently thought the entry door lock on my motorhome was failing (locking the door with a key from outside became very difficult/impossible), but a few squirts of powdered graphite and a few dozen cycles of locking and unlocking and the problem has gone away!
I've never had a problem with a lock failing due to graphite causing excessive wear and premature part failure. I've had plenty of locks go bad which were never lubricated though :)
Graphite will oxidize aluminum when exposed to oxygen
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