Knew an engineering degree would be useful for something one day
Steel is typically and principally alloyed with Chromium to make it a Stainless grade. Copper is added to some variants to improve corrosion resistance, - more common in steels used for marine applications.
Pure (24 Carat) Gold is often alloyed with Copper, Nickel, or Silver to give the lower carat golds mostly available in shops (Rose Gold may up to 50% Copper) depending on the desired colour.
In the EU the use of Nickel in jewellery has been restricted because of known skin reactions but if the item originated outside the EU then it may be present.