New Techniques Expose Fake Coins Faster

Their study found that when coins are exposed to a pH of between four and 6.8, which is commonly found in sweat, particles from the surface became loose and fell off. This exposed where dirt was originally glued to that could be detected through scanning electronic microscopy, energy disbursive X-ray analysis and X-ray disfraction.

“Ions that released from coins in artificial sweat solution were analysed. The surface morphology was investigated for the coins before and after immersion in artificial sweat solution,” they said in an International Journal of Electrochemical Science article called Corrosion Behaviour of Coins in Artificial Sweat Solution: A Review.

“Coin materials and time of circulation affect their loss of the original appearance, colour and clear pits of their surfaces. This behaviour [is] mainly caused by human sweat that gradually destroys the coins surface.”

Researchers achieved optimal results after soaking for at least one week because this helped release more concentrated nickel ions (Ni-ions) than shorter periods. “The released Ni-ions concentration from the minted 25 pound Egyptian coins exceed the safe limit of ni[ckel] release. Open-circuit potential showed clearly a possibility of the formation of oxide film on the surface of 25 pound and 50 pound coins thus 25 pound coins are more active than 50 pound coins in artificial sweat solution,” they said.