E-Z-Est Cleaner - Is It Meant For Clad Coins?

That is true it isn't acidic, is is basic, and a base can be just as corrosive as an acid.

Best to rinse your coins off by pouring water over them not by dipping them in bowls. Also E-Z-Est is specifically for silver not for clad coinage.

E-z-est a.k.a. JeweLuster is, as noted above, specifically designed for removing tarnish from silver coins. It contains sulfuric acid and thiourea. "Tarnish" is silver sulfide, and silver sulfide readily reacts in such a solution, forming a silver-thiourea complex which is water-soluble, so the tarnish simply dissolves away. Hydrogen sulfide gas is also formed as a by-product, which is why silver-coin-dippers will often notice a "rotten egg smell" as they work. Silver metal is relatively resistant to such acids, so the bare metal of a silver coin is almost* unaffected by it.

* - the use of tarnish-removing chemicals on silver coins can be proven in a court of law, if and when people are inclined to do so.

However, dilute sulfuric acid will readily dissolve copper and nickel metal, as well as alloys thereof. The presence of thiourea is irrelevant in such a circumstance, it is only the sulfuric acid that will react. Dilute sulfuric acid attacks and dissolves the metal directly, though of course it will also attack and dissolve any corrosion products on the coin's surface. The end result will be an acid-etched coin, which will look duller and less attractive than a coin that was never tarnished-and-dipped. The acid will also create microscopic pits and bumps in the coin's surface, increasing the surface area of the coin. This has the result of "activating" the surface, so that it will tarnish much faster in the future.

It is a shame that so many don't realize that when a coin is cleaned, it is not only dirt that comes off, but a bit of metal too.