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<p>[QUOTE=&quot;Pete Apple, post: 26153821, member: 103982&quot;]I have been studying plating dynamics for copper-plated zinc cents.</p><p>I summarized some of my findings in a paper titled PLATING SURFACE CORRUGATION.</p><p><br /></p><p>Link:</p><p><a href="https://www.cointalk.com/threads/plating-surface-corrugation.417006/" class="internalLink ProxyLink" data-proxy-href="https://www.cointalk.com/threads/plating-surface-corrugation.417006/"><b>https://www.cointalk.com/threads/plating-surface-corrugation.417006/</b></a></p><p>&nbsp;</p><p><br /></p><p>The paper seeks to examine the causes of the ridges and valleys seen on many copper-plated zinc cents.</p><p><br /></p><p>One of my unanswered questions was the effect of the strike on a planchet with corrugation, since the fact that unstruck planchets may exhibit the ridges and valleys frequently found on plating surfaces. To me, it is counterintuitive that a strike would not completely obliterate any existing ridges and valleys.</p><p><br /></p><p>However, because of a question I received, I recalled one experiment that Ken Potter and I worked on jointly:</p><p>We were working on Rockwell Test Marks.</p><p><a href="https://www.coincommunity.com/go/link.asp?target=https://conecaonline.org/rockwell-hardness-test-marks-on-lincoln-cents/" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://www.coincommunity.com/go/link.asp?target=https://conecaonline.org/rockwell-hardness-test-marks-on-lincoln-cents/" rel="nofollow">https://conecaonline.org/rockwell-h...ncoln-cents/</a></p><p><br /></p><p>I had a Rockwell Test performed on a struck copper-plated cent. That the test was performed after the strike is evident from the pressure ridge around the mark - a strike will obliterate the pressure ridge. It turns out that a strike does even more - it deforms the mark extensively!</p><p><br /></p><p>Ken took that coin some years later and had it struck into his 50th Anniversary of Serving Collectors Medal. The following photo composite shows the effects of that strike.</p><p><br /></p><p>Notice that the surface of the field of the coin is NOT totally flattened, which I would have expected it to be!</p><p><br /></p><p>This tells me that the Ridges and Valleys are quite capable of surviving the strike! This also suggests that the greatest portion of the energy of the strike is dedicated to forcing metal into the recesses on the die to form the devices rather than onto the fields.</p><p>[ATTACH=full]1669915[/ATTACH] [ATTACH=full]1669916[/ATTACH] [ATTACH=full]1669917[/ATTACH][/QUOTE]</p><p><br /></p>

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