I did, hence why I asked. I should have been more clear, and asked "are platinum plug electrodes made of platinum" im guessing that's why they don't wear away as fast?
That is more clear; and yes platinum plug electrodes are made of platinum, and iridium plug electrodes are of iridium--with a caveat.
On a typical "single" precious metal plug only the center electrode is made of the precious metal (be it platinum or iridium), the side electrode will be nick/chrome alloy. "Double" platinum plugs have a precious metal center electrode and a precious metal insert on the side electrode.
"Why?" you ask.
In a classic single coil distributor/plug wires type system the established convention was that the center electrode would be negative (electrically) relative to the side electrode (ground), this is called a negative firing
system. COP based systems also follow this convention.
Electric current (electrons) flow from negative to positive (Volta got it wrong), this means that in a negative firing ignition system electrons flow from the center electrode to the side electrode.
This electron flow carries with it molecules of the negative (center) electrode material which are deposited onto the side strap, eroding the center. So for best plug life the center electrode material needs to be made of something resistant to this erosion--tungsten and then nickel/chrome alloy fit this bill, with platinum and iridium being even better.
With the advent of distributor-less ignition systems it became possible to fire two plugs from each coil, often using coil packs, often containing two or more coils. In Ford's EDIS (Electronic Distributor-less Ignition System) used on the V8s before the COPs there were two coilpack, each containing two coils; each coil fires two plugs at a time. One producing the active spark (actually igniting a fuel charge) and the other producing a "wasted spark", firing near the top of the exhaust stroke.
These paired plugs also fire in reverse polarity relative to the other, one negative firing the other positive firing, as shown below:
In the diagram the #5 plug is firing in conventional "negative" polarity (current flows from the tip to the side electrode), the #1 plug in reverse "positive" polarity (current flows from the side to the tip electrode). Obviously for the reverse polarity plug the side electrode must also be made of a material resistant to erosion, the same material as the center if both plugs are to have the same service life.
OEM plugs for wasted spark systems are often cylinder specific having either a center or side electrode of precious metal. This is mentioned (but not explained) in the '96 through '98 Mustang Owner's manuals:
Note that the specified replacement plug are type AWSF-32PP, the PP
meaning double platinum. In the note below the table there is a caution that plugs removed for inspection must be put back in the same cylinder from which they were removed; and that for the 4.6L 2V the #1, #2, #3, and #4 plugs have a PG
, Platinum Ground
, suffix; while the #5, #6, #7 and #8 plugs have a P
, Platinum [tip]
This saved Ford a few cents per plug (* 1,000,000 cars a year = $40,000 to $50,000). In the the aftermarket where unit cost is less of an issue it doesn't make sense to stock two types of plug for the same vehicle so they are all double platinum.
All of the above is only so for wasted spark systems, there is no need to ever use double platinum plugs in a '99 through '04 GT...