Graphite Aluminum Compatibility:
Extreme potential for galvanic corrosion to the aluminum. Graphite used on aluminum, magnesium, zinc, cadmium may cause galvanic corrosion. It is best suited for Inconel, stainless, and titanium alloys.
"...shown conclusively that graphite in a resin-bonded solid film lubricant is deleterious from the point of view of corrosion protection provided by the lubricant... To use graphite is to invite corrosion difficulties in the presence of moisture."
Rock Island Arsenal Laboratory, Technical Report, Dry Lubricants and Corrosion, Prepared for Presentation at the Annual Meeting of the Society of Automotive Engineers, Detroit, Michigan 14-18 January 1963. Francis S. Meade and George P. Murphy, Jr.
Aircraft mechanics traditionally did not use graphite. They did not use graphite anti-seize and they did not make graphite pencil marks on aircraft parts. I remember using a "grease pencil" to mark aircraft engine parts instead of a "lead pencil". Graphite does not contact aluminum.
So for all of you younger aircraft mechanics -throw away that can of graphite anti-seize that you purchased at the automotive store. It will get you in trouble and it looks very unprofessional.
"...Graphite is cathodic to all structural metals and will generate cathodic corrosion in the presence of moisture, especially if the graphite is applied in dry form."
FAA AC43.13-1B Acceptable Methods, Techniques, and Practices.
"...Packings, gaskets, and lubricants containing graphite can lead to severe galvanic corrosion of copper alloys and stainless steels in saline waters and should be avoided..."
Gaskets and packings containing carbon or graphite are easily identified: they are black.
Materials for saline water, desalination and oilfield brine pumps, 1st ed,. 1988, NiDi Reference book No. 11 004.
Graphite Requires Moisture
Graphite is a lubricant only in the presence of moisture. When dehydrated it is a slight abrasive. For example, carbon brushes for aircraft accessories often have moly added to increase brush life. Pure carbon brushes wear extremely fast at high altitudes where there is no moisture. The same is true for a dry graphite lubricant, at high altitudes where there is no moisture, the graphite stops being a lubricant and becomes abrasive..
The fact that graphite requires moisture limits its maximum temperature to the boiling point of water. Remember that the boiling point lowers with altitude.
Graphite's requirement for moisture also affects vacuum pump life. Dry vacuum pumps use carbon vanes. Vacuum pumps in dry climates, such as Arizona, wear faster than vacuum pumps in wet climates, such as Florida.
--exception to the rule --
There's always one.
Graphite and water anti seize has been used and recommended for aircraft spark plugs for over 50 years. Other anti-seize that contains metallic particles have been avoided because of the chance that the anti-seize particles may get into the combustion chamber, create a hot spot, and cause destructive pre-ignition.
Years ago mica anti-seize was commonly used for spark plug anti-seize and it probably has better properties than graphite and water. However, there is a problem in changing anti-seize types; you change the torque tension relationship. Published torque values in aircraft spark plugs are based on using the manufacturer's recommended anti-seize. Use a different type of anti-seize and the required torque to achieve the proper amount of tension will change by an unknown amount.
