Etruscan jewelry
The combination of metals was a basic technique. Essentially, there is no such thing as 24 carat gold jewelry. Massive gold is the most malleable metal. It is almost like wax. In order to have jewelry that can pass the test of time and gravity, the Etruscans had to combine their gold with other metals.
Copper in architecture
Metals are ranked according to galvanic numbers as a qualitative measure of their nobility. These numbers qualify the resistance to corrosion of any metal when in contact with other metals. A larger difference in the galvanic number between two metals in contact with each other indicates a greater potential for corrosion.
The galvanic numbers of the most common metals used in construction are ranked as follows: 1. aluminum; 2. zinc; 3. steel; 4. iron; 5. stainless steel - active; 6. tin; 7. lead; 8. copper; 9. stainless steel - passive.