Platinum
Pure platinum is a lustrous, ductile, and malleable, silver-white metal. Platinum is more ductile than gold, silver or copper, thus being the most ductile of pure metals, but it is less malleable than gold. The metal has excellent resistance to corrosion, is stable at high temperatures and has stable electrical properties. Platinum does oxidize, forming PtO, at 500 °C; this oxide can be easily removed thermally. It reacts vigorously with fluorine at to form platinum tetrafluoride. It is also attacked by chlorine, bromine, iodine, and sulfur. Platinum is insoluble in hydrochloric and nitric acid, but dissolves in hot "aqua regia" (A mixture of nitric and hydrochloric acids), to form chloroplatinic acid, HPtCl.
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.