Here are the facts:
- Palladium is less expensive than platinum
- Palladium weighs less than platinum
- Palladium belongs to the same chemical group as platinum and therefore has similar chemical behaviour
- Palladium is more difficult to work with in jewelery
Platinum and palladium are indeed quite similar. They have similar color as both are naturally white. Platinum has traditionally been prized as a metal in jewelery because of its resistance to wear and tarnish. Therefore, the focus of this discussion is going to be on these two less well-known aspects.
Is palladium harder than platinum?
The way you determine how a material holds up to wearing is by looking at it’s hardness. Now for a non-engineer, it may be confusing to learn that there are several types of hardness measurements.
An easy way to think about it is to put it in real terms. When we have a ring, we are really just concern about two things.
- How well does it resist scratching against something?
- How well does it resist an indentation upon banging it on something?
The Mohs hardness test tells us about scratching, and the Vickers hardness test tells us about indentation.
The Mohs hardness of palladium is 4.75 and the Vickers hardness is 461MPa. The Mohs hardness of platinum is 4.25 and the Vickers hardness is 549MPa. This means that palladium will scratch platinum but platinum holds up against impacts more.
In my opinion, the Mohs hardness is more important because scratching is more likely to occur than indentation during everyday wear. And the Vickers hardness being an absolute scale tells you less about real world performance. Again, to a non-engineer, Megapascals are not very meaningful.
So to put it into context, 400MPa is around the pressure that is inside the chamber of a 1910 .50 Browning Machine Gun when it discharges. On the other hand, the average impact pressure of a fist punch is about 300kPa, which is over 1000 times less pressure than what is required to indent palladium.
Is palladium more resistant to tarnish than platinum?
When we talk about tarnish, what we are actually referring to is the chemical process of oxidation. Oxidation is what is responsible for both tarnishing and the formation of a patina. As a chemical process, the rate of oxidation depends on the temperature, time, and the oxidising agent.
Now both palladium and platinum does not react with the oxygen in air under normal temperatures. Add a little heat (400-500 degrees Celsius) then you will begin to see a thin layer of oxidation. You will only start noticing a difference if you raise the temperatures even more. For example, palladium will tarnish readily at around 850 degrees Celsius.
Platinum on the other hand when heated to similar temperatures where the metal begins to glow red-hot will form only an invisible thin layer of oxide. It is therefore said that platinum is more resistant to tarnish.
In my opinion, the difference between tarnish and patina is in name. Tarnish is given a negative connotation and patina is associated with being positive. Oxidation is called a patina when it occurs throughout the metal and forms an aesthetically pleasing protective layer of oxide. There are different confusing accounts of the differences between tarnish and patina but the underlying chemical process is the same.
The confusing difference is probably because of the differences between tarnish and patina when referring to sterling silver. Tarnish usually refers to the oxidation that occurs when you forget to polish your silver. A patina is usually associated with what is observed in an antique look where the silver has tarnished in areas that are difficult to polish and thus the patina helps reveal the detail in the metalwork.
In palladium and platinum, tarnish doesn’t occur easily and therefore the word patina is used to describe the oxidation over time. If you have read that palladium has a worse looking patina than platinum over time, this is probably referring to a significant long period of time without polishing and the reason for this is because the patina on platinum is almost invisible.
So the answer to which is better, platinum or palladium is neither is better than the other. Palladium is more resistant to scratches but platinum doesn’t form any visible signs of tarnish over time. In my opinion, palladium represents better value for money. Even if the metal tarnishes after a while, it can be re-polished easily to restore it’s original whiteness.
A jeweler will find palladium harder to work with because it is harder and stronger so may charge more for their services, but this is more than made up for by the lower cost of the material itself. Platinum on the other hand is more well-known even though palladium has been used by jewelers for almost a century now. In the end, you will win with either because platinum and palladium are increasingly becoming important in the automotive industry, as most of these metals go into cars either in catalytic converters or in fuel cells. Their importance and their rarity; their usefulness and their beauty will all be factors that will ensure that the prices of the platinum group of metals increase in the foreseeable future.
For a comparison of platinum against other metals used in jewelery please read my tutorial on choosing a metal for an engagement ring. You can also find some helpful tips on choosing an engagement ring setting here.