This may have been discussed here before, but I can't find it. IMHO, CuNi clad coins look cheesy. If they're going to be 90% copper and 10% nickel, or whatever they are, why not just melt it all together so it looks like (and is) one solid alloy? Like a nickel (the coin). There must be a reason - I would think it would be cheaper to manufacture the blank planchets... Are their any metallurgists out there who could tell us what color a blob of metal that is 90% copper and 10 nickel would be?
Actually the US is one of the few countries that does this. Quite a few world coins "sandwich" their metals. It's actually a good idea, really. Imagine if they were solid edged? That would be a pain to sort through rolls, looking for silver.
I'm not sure it would be cheaper manufacturing it as an alloy and may not be practical. The first thing to consider is how easy it would be to impart coin designs on an alloy versus a core/layer sandwich. The alloy may be too much of an alloy and over all strike quality would suffer. Cost wise paying for 90% copper and 10% nickel would be the same no matter how you mixed them. Cents would still be around 3cents and nickels around 7 cents to manufacture. Remember the metal costs, the mint's overhead (cost of paying employees, machinery costs, upkeep, utilities, counterfeiting tech. etc) and shipping bags/rolls to banks all over are the real production costs not the making and stamping of the planchets. I'm not a metallurgist but my guess is the nickel would lighten the copper from a "red" color to a pinkish color almost like a rose gold color as most rose gold is white gold (which is yellow gold and most commonly nickel) mixed with pure copper.
I wrote a term paper for a high-school class in 1964 on this subject. When the price of silver went up due to the Vietnam war inflation, the US Government had to remove silver from coins and replace it with another metal. The coins had to work in vending machines, most of which "tested" coins using an electrical current. Copper and silver have similar electrical properties, so copper was used. The copper-nickel clad covering was to make the coins look somewhat "silver". Got an 'A' on the paper.
In addition to the electrical transmission properites mentioned above the Nickel outer layers are harder than an alloy would be and increases the life of the coin by wearing slower.
Pink quarters and dimes and Halves ? We probably would have lost the war if we had pink coins ! ....oh wait !
Humm - didn't think about the longevity aspect. Then if we were really worried about that, there would be no dollar bills. Pink coins - those would work in San Fran and Seattle's Queen Anne Hill area. Might be shunned in other areas... Oh, and pink would solve the 'looking for silver' problem too!
Ironically it was likely the testimony before Congress of a representative of the vending industry that led to clad coinage. Congress primarily wanted a metal that would fool the public into believing there was no change and that would work in vending machines. In those days vending was a large part of the economy because coins could buy almost any small product. After many years of inflation we don't have coins that can even buy a pack of gum. The representative testified that the most dangerous counterfeits were cladded metals because they could fake the electronic signature of silver. After many efforts to find a cheap alloy they settled on the one we still use. In those days they didn't have rollers or presses strong enough to complete the bonding of the three layers of metal so they were forced together with hydraulic presses and then dynamite was exploded above them to complete the process. Unsurprisingly there was a lot of trouble with layers separating and debonding in the early years. So far as I know all the clad planchets for foreign coins are made by the same manufacturers who make the US planchets. I can't thing of any coins except those made on quarter size clad. The total mintage of these is not extremely high though.
