Spark plug anti-seize compound

[Squito]

In another post regarding the use of thread lock on spark plug heli-coil inserts (Spark Plug Heli-coil Insert), several commenters made mention of using copper-based thread anti-seize instead of the previous long-time-in-use graphite compound. I learned and used graphite thread anti-seize, as it was standard practice in the '70s, '80s, and 90's. In researching the use of graphite versus copper thread lube on spark plugs, Lycoming specifically states in SI 1042AH and the Overhaul Manual to NOT USE a graphite-based compound for spark plugs threads.

It appears the change from graphite being okay to the not being okay occurred sometime after 2002 (SI 1042X dated 2002 and prior does not have the restriction). Neither the SI or the overhaul manual explains WHY the change. So I asked Lycoming Technical Support, as I have a Lycoming engine.

Their response was that mechanics should use a copper based anti-seize and not use a graphite compound because graphite sometimes promotes electrolytic corrosion that would cause the steel plugs to bond to the heli-coil, ripping the heli-coil out when the plugs were removed. Copper is not reactive that way.

So there you have an explanation of the reason for the copper-based anti-seize. Hope it is of value and helps prevent problems down the road for owners and operators.