1964 Nickels Wrecked With Tarn-X

If it makes you feel any better those coins are most likely not high value...

unless those were key dates or silver War Nickels consider yourself lucky..otherwise only worth about 5 cents then..

Many substances can change the color of coins. Some dishsoaps change coins blue for example. Tarn-X is basically for cleaning metals of all types. However, pending on if the stuff you used was also used prrviously for something else, could have left a layer of something on the coins too. Also, it is obvious that the Tarn-X reacted with Nickel/Copper.
It is possible to make them look like a Nickel again but might mess them up even more and the cost is really not worth the effort. If you feel like experimenting, you could try dipping them further in Olive Oil, boiling them in water on the stove, soaking them in Vinegar or even Lemon Juice. Some people use Tomato Juice, Lime Juice, battery acid or Acetone too. You could check to see if there is any Jewlery cleaner in the house and use some of that.
HOWEVER, since some are 1964, I'd just spend those.

The only silver nickels made were from 1942 to 1945, they can be easily identified by the large mint mark over the dome of Monticello.

pinky. As you saw, you'll always get helpful advice from the forum members.

Tarn-X is Dangerous & Destructive!

As a specialist in silver restoration, conservation, and preservation, I have many years of knowledge about chemical dips, especially Tarn-X. I routinely receive objects for refinishing due to damage from this horribly destructive product.

Tarn-X works by dissolving the tarnish (and silver!) on an object at an accelerated rate.

Tarn-X will quickly remove factory-applied patinas (if left in the solution for more than a few seconds) or gradually (if dipped quickly each time the object requires cleaning). You'll notice a soft white surface develop over time.

Tarn-X will quickly strip the shine from silver, leaving a dull, lifeless appearance.

Tarn-X will cause pitting of the object's surface. These surface defects will act like a sponge and more readily absorb tarnish-producing gases and moisture. The object will eventually require professional polishing to restore the original finish.

Tarn-X is made up of acidified thiourea (a known carcinogen). Acids are corrosive and will damage silver, niello, bronze, stainless steel knife blades, and organic materials such as wood and ivory.

Tarn-X, when used on objects that have sealed components, such as candlesticks and trophies with hollow feet, or teapots with hollow handles, may leak into the cavity through small holes or imperfections in the joints. At this point, it becomes virtually impossible to wash the chemical out. If you're working on a baby cup with this type of rim, do you really want an infant drinking from it after using Tarn-X?

And these are the results from using Tarn-X: http://www.hermansilver.com/tarn-x.htm.

Cleaning coins is really not the best way to go....One must be careful with what one uses but more on that later.