The one trillion dollar coin; or, “The Simpsons solution”

Apparently someone has been watching back episodes of The Simpsons to take his mind off the current fiscal cliff crisis, and was inspired by the one where Monty Burns has stolen a trillion dollar banknote.  Apparently such notes are not legal under the current rules, but a coin could be as long as it is not composed of gold, silver, or copper.

This has prompted the suggestion that the US Mint could produce a couple of one trillion dollar coins made of platinum or palladium that could be placed in the treasury and provide funds for all the cheques the Administration wants to write.  Some have waxed lyrical about making enough of them to pay off the entire national debt.

The idea is so bad that even Paul Krugman thinks it’s silly: 

KRUGMAN: You can issue — it appears to be legally possible to... 

STEPHANOPOULOS: That are worth a trillion dollars each? 

KRUGMAN: ... to print — to mint a $2 trillion platinum coin, which is ridiculous, but the whole debate is ridiculous, right? If you've got somebody who's holding the American economy hostage and trying to extort policy concessions that they could never actually pass through Congress and that they could never get past the voters, you go for whatever you can do to stop it. But he won't do that.

The question though, why use something as expensive as platinum or palladium if the problem is only the use of gold, silver, or copper? 

Steel is relatively inexpensive, and the corrosion problem could be adequately addressed by using galvanized iron.  The mining, machinery and construction industries use large washers in gal or even in alloys, which would be even better, which could be stamped with the relevant value.

The hole in the middle should not be a problem as there are many examples of coins with a hollow centre.  Actually if the head of the President was stamped on one side the hole might swing some of his opponents in favor of the idea.