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<p>[QUOTE=&quot;-jeffB, post: 4565034, member: 27832&quot;]Zinc is so <i>soft</i> that I&#039;d think a toothbrush would just finish them off. <img src="styles/default/xenforo/clear.png" class="mceSmilieSprite mceSmilie3" alt=":(" unselectable="on" unselectable="on" /></p><p><br /></p><p>Zinc is a really reactive metal. Unlike silver or copper, it reacts with <i>both</i> acids and bases. There may be something that would complex with the oxide layer and dissolve it without attacking the metal, but I&#039;m not enough of a chemist to figure it out.</p><p><br /></p><p>(I found a metal-detecting site that recommends soaking them in dilute sulfuric acid, then rinsing them with sodium hydroxide solution. I wonder if the person who posted that advice has ever actually tried it. Each soak would be <i>dissolving</i> the coin&#039;s surface.)[/QUOTE]</p><p><br /></p>

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