There are three basic electrode materials.
Traditional nickel-alloy electrode materials have good conductivity, but melt at a relatively low temperature and are more easily eroded. To counter the inevitable erosion, the electrode must be made large, and that means more of the combustion chamber is taken up by the electrode.
Platinum is equivalent to traditional materials in its conductivity, but has a much higher melting point and resists erosion much better. The platinum center electrode can be made much smaller, which promotes a stronger, smaller spark. The smaller center electrode allows more room for the flame front to propogate out away from the plug. Platinum plugs are, of course, much more expensive than traditional spark plugs.
Iridium is the king of spark plug metals. It has strength and melting temperature far higher than even platinum. The high melting point means the center electrode can be made even thinner - 0.4mm on the Denso plugs we sell (see picture). The longevity of these plugs is unsurpassed. Iridium is so hard that the electrode must be welded on using lasers; this process, plus the scarcity of the metal, contributes to the plugs' high price. But no plug will last longer than an iridium one.
Sign up to get the latest on sales, new releases and more …