Alloy are relatively similar in size, the atom exchange method usually happens, where some of the atoms composing the metallic crystals are substituted with atoms of the other constituent. This is called a "substitutional alloy". Examples of substitutional alloys include bronze and brass, in which some of the copper atoms are substituted with either tin or zinc atoms respectively. In the case of the interstitial mechanism, one atom is usually much smaller than the other and can not successfully substitute for the other type of atom in the crystals of the base metal. Instead, the smaller atoms become trapped in the
Antimicrobial copper-alloy touch surfaces copper on floors, sinks, push plates, showerheads and doorknobs was evaluated by comparing bacterial loads on these surfaces and on their non-copper counterparts. The number of viable "Staphylococcus spp". organisms on surfaces containing copper and its alloy were reduced by half to one-thirtieth of that on control surfaces, depending upon surface humidity and the frequency of contact. Similar definitive findings were also obtained for "Pseudomonas aeruginosa". Various metals were evaluated for their antimicrobial efficacies, including copper alloys, zinc, nickel, tin, silver, and gold. Antimicrobial efficacies generally followed Lewis acidity values of the various metals. Silver, a prohibitively expensive precious metal,