Rhodium content in a single modern iridium spark plug is very low, typically found in the tip of the electrode as part of an alloy, comprising about 10% to 35% of the small tip material, which often weighs in the milligram range. While some high-performance or aviation plugs may use a higher percentage of precious metal alloys, the actual mass of rhodium per plug is miniscule.
The EDS spectrum from area X-05 shows 90% iridium and 10% rhodium. Here is the precious metal content labeled on the plug.
Recycling iridium from old spark plugs is no small task. Iridium is one of the toughest, most stable metals out there, which makes it ideal for extreme environments but also very hard to extract. That's why the recycling process involves multiple professional stages to safely and efficiently recover it.
Every year, hundreds of millions of spark plugs are replaced. Most of these spark plugs end up in landfills or as scrap steel. The vast majority of these spark plugs also contain precious metals such as platinum and iridium. These precious metals are regarded as scarce and strategic metals for the United States.
Typically, the amount of rhodium in a catalytic converter is anywhere between 1-2 grams, while the amount of platinum ranges anywhere from 3 to 7 grams and the amount of palladium ranges anywhere from 2 to 7 grams.
Platinum is not the only precious metal in your catalytic converter. Palladium and rhodium, both platinum group metals, are also necessary for the converter to work. These metals are found in smaller amounts than platinum, but the average one to two grams of rhodium they contain is still valuable.
The “common knowledge” about rhodium is that it is most commonly found in automobile catalytic converters.
Some plugs include a coating or pad of precious metals to extend plug life. But as a general rule of thumb, all spark plugs utilize a copper core. Gold is an excellent conductor of electricity, which makes it well suited for a performance plug.
Advanced materials like iridium and ruthenium offer significant improvements over traditional metals for spark plugs. These rare elements resist heat, reduce electrode wear, and maintain consistent conductivity for thousands of miles longer. In other words, they help your engine run smoother, longer.
7 Surprising Places to Find Platinum Scrap
The price of iridium per ounce fluctuates but is generally very high, often in the $4,000 to over $5,000+ USD range, making it more expensive than gold due to extreme rarity, limited production, and critical industrial uses, though exact figures vary daily. You can find real-time updates on sites like Metals Daily or Metal.com.
Rhodium is found in platinum or nickel ores with the other members of the platinum group metals. It was discovered in 1803 by William Hyde Wollaston in one such ore, and named for the rose color of one of its chlorine compounds.
While you might imagine that extracting the precious metal content from catalytic converters would be as simple as cracking the converter open and prying the platinum, palladium, or rhodium out, it's actually an incredibly sophisticated process.
The most common types of car parts that contain precious metals are:
An adult human body contains approximately 5 liters of blood, which contains different metals such as iron, chromium, and zinc, as well as about 0.2 milligrams of gold [1]!
Although the underlying metal may be magnetic, the rhodium plating itself is not magnetic. Thus, if you have a piece of jewelry that has been rhodium plated, it will not be magnetic.
Although the quantities vary by model, on average, only one standard catalytic converter contains about 3-7 grams of platinum, 2-7 grams of palladium, 1-2 grams rhodium.
And that's the case even though each catalytic converter only contains roughly 3 to 7 grams of platinum. It doesn't seem like much, but note that the current price for this precious metal is nearly $50 per gram –- more than $1,400 an ounce.
Catalytic converters are targeted for theft because of the precious metals they contain, such as platinum, palladium, and/or rhodium which can yield fast cash to a thief.
The iPhone has 0.015g of palladium in it. Palladium is sometimes used in jewelry and is hypoallergenic. The element takes its name after the asteroid Pallas, which comes from the Greek goddess of wisdom, Pallas. Palladium can absorb hydrogen like a sponge; it absorbs up to 900 times its own volume.